Ferro Cement Tanks for Water Storage

Design, Tools, Materials, and Construction

Art Ludwig

Summary: A do-it-yourself guide to designing, building, and maintaining ferro cement water tanks and cisterns. Includes 100 pages of water storage design information, 24 pages of detailed building instructions for several styles of ferro cement water tanks.



How to Build Ferro-Cement Water Tanks

Author: Art Ludwig, published by Oasis Design. 2005. 8.5x11, 125 pages, 43 figures, 128 photos. ISBN 0-9643433-6-3. $19.95



Not another stuffy engineering manual—a very good book that anyone can read. It is especially suited for operators of small water systems. On the average water system, this book will pay for itself a hundred times over in errors avoided and maintenance savings.
—Zane Satterfield, P.E., National Drinking Water Clearinghouse

Practical design solutions, comprehensive illustrations, and plenty of photos—a thorough treatment of a topic that's vital to our survival.
—Claire Anderson, Home Power Magazine, Mother Earth News

All sorts of alternatives to your standard plastic water tank, accessible by anyone from homeowner to builder to civil engineer.
—Amy Wynn, Builders Booksource

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Ferro cement water tank shaped like an urn
Ferro cement water tank shaped like an urn

How to Make Ferro Cement Tanks

Ferro cement tanks consist of an armature (framework) of steel reinforcing, which is then covered with a sand-cement plaster. They offer complete flexibility in shape. They have a long life, are cost-competitive when contractor-built, and are owner-buildable in both industrialized and non-industrialized countries.

This section describes how to build ferro cement tanks with various techniques, to a variety of standards and sizes from 250-30,000 gal (1-115 m3). With the aid of an engineer you could adapt the plans up to a 100,000 gal (380 m3) tank. For more on the advantages and characteristics of ferro cement tanks, see Tank Materials/ Ferro Cement p. 41.

The existing literature on ferro cement tanks is sparse, and each document is narrowly focused: one particular size of one design, or a variety of designs but all for the context of non-industrialized nations. The heavy-duty ferro cement construction technique described here—which is suitable for large tanks—has not been described in the literature before to my knowledge.

This appendix—practically a book in itself—is unique in that it describes the full range of ferro cement techniques in one place, and reconciles some enormously disparate opinions and techniques into a coherent formulary.

Heavy-duty Ferro cement Tank Section showing steel armature, center access, inlet, outlet
Heavy-duty ferro cement tank (section)

From procedures for ultra-light-duty tanks that use the absolute minimum of material, to tanks built successfully by native women with no construction experience, to detailed procedures for building large tanks to last a lifetime—you can glean the best approach for your context.

In the do-it-yourself, innovative spirit of ferro cement, this appendix gives you not only recipes but numerous variations and ideas for promising innovations, so that you can follow a recipe or concoct your own to suit:

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Chapter 1: Thinking About Water

Why Store Water?
Cover Peaks in Demand • Smooth Out Variations in Supply • Provide Water Security in Case of Supply Interruptions or Disaster • Save Your Home from Fire • Meet Legal Requirements • Improve Water Quality • Provide Thermal Storage and Freeze Protection • Enable a Smaller Pipe to Serve for a Distant Source
Design Principles
Water System Design • Performance and Security Standard • Running Water People, Still Water People • Separate Handling for Different Qualities of Water • Design Horizon • Design for Failure, Design for Change • Where the Stuff in Water Ends Up • What Do You Have? What Can You Find?
How Water Quality Changes in Storage
Ways to Improve Water Quality in Storage • Hazardous Disinfection Byproducts• Effects of Heating • Bacterial Regrowth • The Problem of Leaching • Water Age • How to Test Stored Water

Chapter 2: Ways to Store Water

Source Direct (No Storage)
Store Water in Soil
Store Water in Aquifers
Store Water in Ponds
Store Water in Open Tanks, Swimming Pools
Store Water in Tanks

Chapter 3: Water Tank Design

Tank Components Overview
Situating Water Tanks
Elevation • Stability of Soil and Slope • Aesthetics, Sacred Spots • Security • Buried Storage
Sizing Water Tanks
Sizing a Tank For Demand Peaks which Exceed Flow • Sizing a Tank When You Have Limited Water Supply with Scheduled Use • Sizing a Tank to Cover Use During Interruptions in Supply • Sizing a Tank When Production Is Intermittent • Sizing a Tank for Firefighting • Size and Structural Integrity
Tank Shape
Tank Materials
Materials Situations to Avoid • Glass • Ferrocement • Galvanized Steel • Stainless Steel • Porcelain-Bonded Carbon Steel • Brass • Copper • Aluminum • Rock and Mortar • Concrete • Brick • Clay • Wood • Plastic • High Density Polyethylene (HDPE #2) • Ethylene Propylene Diene Monomer (EPDM) • Fiberglass (Glass Fiber-Reinforced Polyester, GRP) • Epoxy-Coated Steel or Concrete • Masonry in and over Plastic • Galvanized Steel with Plastic Membrane • Interior Membranes for Repair • Plastic Bladders • Goat Bladders, Leather, etc.
Tank Footings and Floors
Tank Roofs
Water-Harvesting Roof
Tank Costs
Really Cheap Storage
Regulatory Requirements
Zoning • Architectural Guidelines • Building Department • Fire Department • Health Department
Hazards of Stored Water & How to Avoid Them
Drowning • Structural Collapse • Flooding • Pestilence • Toxic Contamination • Liability Exposure
Water Tanks for Special Applications
Pressure Tanks • Break Pressure Tanks • Hot Water Storage • Tanks for Transporting Water

Chapter 4: Common Features of Water Tanks

Service Access
Tanks with No Drain • Drain Location and Orientation
Air Vent
Sunscreen and Shade

Chapter 5: Optional Water Tank Features

Inlet Meter, Filter, Gauges
Inlet Float Valve
Inlet Combined with Outlet
Inlet Aerator
Inlet Diffuser to Improve Settling
Outlet Screen or Filter
Variable Height Outlet
Outlet Float
Water Hammer Air Cushion
Level Indicators
Drain Extension or Baffle
Outlet and Overflow Curves
Pump Controls, Alarms, and Switches
Sand Filter
Multiple Tank Management
Freeze Protection

Chapter 6: Emergency Storage

How Much Emergency Water Do You Need?
Emergency Storage You Already Have
Long-Term Storage in Small Containers
Protecting Stored Water
Systems for Firefighting

Chapter 7: Examples of Storage Systems for Different Contexts

Poor Surface Water Quality, Limited Groundwater
Only Stored Water in Dry Season, Hydroelectric in Wet Season
Creek Direct with Remote Storage and Sand Filtration
Very, Very Low Pressure
Simple Jungle Eden
Rural House with Well
Urban Apartment
Swank Suburban House

Appendix A: Measurements and Conversions

Appendix B: Tank Loads and Structural Considerations

Appendix C: More About Plastics

Appendix D: How to Make Ferrocement Tanks

Ultra-Light Ferrocement over a Form: Jumbo Thai Jar Plans
Ultra-Light-Duty Ferrocement Description
Light-Duty Ferrocement Plans
Medium-Duty Shaped Ferrocement Photos
Heavy-Duty Ferrocement Plans
Tools • Materials • Labor • Design • Site Prep • Grade for the Floor • Drain • Floor and Inside Wall: Welded Wire Mesh • Floor and Wall: Rebar • Inlet, Outlet, and Overflow Hardware • Wall Outer Welded Wire Mesh, First Layer of Lath and Hardware Cloth • Lift the Whole Thing Up and Get Ready to Pour • Pour the Floor • The Roof, Cool Shapes, Ladder • Lath and Hardware Cloth • Plaster Prep: Roof Supports, Seal Door • Plaster the Whole Tank • Keep It Wet • Color and Seal It • Fill It


^ Top ^ | Reviews | How to make ferro cement tanks | Table of contents | Figures | References | Index |Water Storage Extras


Sample Figures & Photos

Natural rock-shaped, stone colored, ferro-cement tank
Ferrocement water tank shaped like a boulder


Tank Inlet, outlet, access, mosquito screen, vent, drain, sump, firefighting reserve, hydrant set aside
Common features of water tanks


brass or galvanized, PVC outlet/drain, dedicated drain, valve, low tech drain and outlet
Drain Construction Detail



^ Top ^ | Reviews | How to make ferro cement tanks | Table of contents | Figures | References | Index |Water Storage Extras


References & Further Reading

See Water Storage References


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See also:

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Appendix D: How to Make Ferrocement Tanks Ferrocement tanks consist of armature (framework) of steel reinforcing, is then covered sand-cement plaster. They offer near-complete flexibility in shape. They have long life, are cost-competitive contractor-built, are owner-buildable in both industrialized non-industrialized countries. This section describes how to build ferrocement tanks various techniques, to variety of standards sizes from 250-30,000 gal (1-10 m3). aid of engineer you could adapt plans up to 100,000 gal (380 m3) tank. more on advantages characteristics of ferrocement tanks, see Tank Materials/ Ferrocement p. 41. existing literature on ferrocement tanks is sparse, each document is narrowly focused: one particular size of one design, or variety of designs but all context of non-industrialized nations. heavy-duty ferrocement construction technique described here-- is suitable large tanks--has not been described in literature before to my knowledge. This appendix--practically book in itself--is unique in that it describes full range of ferrocement techniques in one place, reconciles some enormously disparate opinions techniques into coherent formulary. From procedures ultra-light-duty tanks that use absolute minimum of material, to tanks built successfully by native women no construction experience, to detailed procedures building large tanks to last lifetime--you can glean best approach your context. In do-it-yourself, innovative spirit of ferrocement, this appendix gives you not only recipes but numerous variations ideas promising innovations, so that you can follow recipe or concoct your own to suit: Plans Jumbo Thai Jar, 800 gal (3 m3) light-duty cistern, can be adapted to make containers of this shape from 250-800 gal (1-3 m3). Description of ultra light-duty ferrocement cisterns up to 3000 gal (11 m3) in size in non-industrialized world. Plans light-duty ferrocement 10,000 gal (38 m3) cistern, adaptable inexpensive, non-industrialized nation-style cisterns from 500-10,000 gal (1.9-38 m3). Construction photos of medium-duty, urn-shaped, ferrocement cistern of 3500 gal (13 m3), can be used in conjunction heavy-duty ferrocement construction plan to guide construction of medium-duty construction cisterns from 500-15,000 gal (1.9-57 m3). These also illustrate how ferrocement can be used to make creative shapes details. Detailed plans heavy-duty ferrocement construction of 30,000 gal (110 m3) cistern, can be adapted to tanks from 3000-30,000 gal (11-110 m3) capacity, aid of engineer, tanks up to 100,000 gal (380 m3). suggest you read this whole appendix before designing anything. You'll see huge difference that performance standard context make (see p. 4), even bigger difference that tank size makes. This will help you to make perfect design adaptations your context. heavy-duty ferrocement technique, is by far most complicated, has most detailed instructions drawings. Much can be learned from that section that will apply to simpler projects. example, there is complete tool list there. (All tools on that list don't have asterisk are needed other methods as well as heavy-duty ferrocement.) Dont Get in Over Your Head Ferrocement requires certain amount of manual skill, any big construction project requires certain amount of organization management skill. Structural sensibility is great help, too. (Reading Appendix B on structural considerations is highly recommended, especially big tanks. Difficulties go up dramatically size of tank.) instructions we offer here are fairly detailed, will give you enormous boost over figuring this stuff out on your own, or from any other source we know of. However, in project of this nature, there is still going to be plenty of stuff you're just going to have to figure out. If you don't feel confident about taking on tank-building project after reading this section, suggest you consider buying or salvaging tank instead of attempting to build one. If you feel only modestly confident, suggest you start modest-sized tank--say 1000 gal (3.8 m3)-- see how that goes before sinking tens of thousands of dollars into construction of huge tank. Design Innovation Ferrocement construction is relatively unexplored field, open innovation improvement. As synthesized wide variety of ferrocement techniques to create this appendix, cross-pollination between different techniques occurred. Some sources had, example, brilliant structural analyses; others had ingenious time-saving construction techniques. 've exercised my best design discretion in taking insights from one source applying them to other techniques. This is how 've handled it: Unequivocal improvements low likelihood of significant implementation difficulties have been put into main narrative drawings. In actual practice, there may be some minor differences. (If you think you've run into one, hope you'll let us know.) Promising but more experimental improvements that may require more than usual level of head scratching to build successfully are given in form of sidebars separate drawings. These prospective improvements have mostly been done in some form, but often not at same scale or together in same tank. example, people have made buried half-sphere tanks in Africa, people have made tanks hemispherical roofs in California, but to my knowledge no one has put two halves together to make totally spherical ferrocement tank. Would some major unanticipated problem be encountered making sphere? Seems unlikely, but there certainly could be. You?ll have to be ultimate judge of advisability of these innovations your project. see this as two-way forum innovation. hope you will take good photos of your project let us know what worked didn't, what new ideas you come up . We'll pay you anything we broadcast through subsequent editions of this book or our website. (You can also check oasisdesign.net/water/storage updates to this section.) Ultra-Light Ferrocement over Form: Jumbo Thai Jar Plans This plan from Intermediate Technology Development Group18 is construction of 800 gal (3 m3) tank. It can be scaled to build tank sizes from 250 to 800 gal (1-3 m3). shape is extremely efficient structurally use of materials, it's beautiful, too. This construction system has been highly successful in non-industrialized nations, especially Thailand, there are millions of 250 gal (1 m3) version of this tank. It can be done minimal masonry skills. technique common in non-industrialized nations is to use form backing. form enables minimally skilled masons to do work, enables mix to go on more thickly evenly, helps slow curing (one side is kept from losing water by form, you can wrap other plastic). There are many form systems, used tanks of up to few thousand gal (10 m3). One form system involves pouring concrete between two sets of steel shutters (see photo, p. 44); another involves stretching chicken wire thick wire over corrugated galvanized one-sided form. only drawback of using form is that you've got to make it, economics are better if it can be reused many tanks. My favorite form system is Thai Jar, incorporates shape strength-enhancing compound curves, has narrower diameter near bottom to reduce hoop stress. form is so simple that it could make sense even if you're only making one tank. In sizes of 250 gal (1 m3) smaller, it can be made without steel reinforcement. In sizes of 55 gal (200 L) smaller, it can be made in same shape out of fired clay. Sew Mold mold (form) is made of 15 meters of canvas 1.2?m wide, consisting of five side panels 1 floor panel sewn together strong thread overlaps of 10 cm on all joints (see Fig 33). To make mold, start by drawing side panel in full size on canvas cut it accordingly. Use this side panel to mark other four side panels cut them. Finally, cut floor panel, then sew all six panels together. Make space string to be pulled tied manhole at top of mold. Foundation jar edge should be situated 90 cm from wall of house (if it is to be used rainwater harvesting). radius of foundation is 75 cm. Draw circumference of foundation using string tied to peg at center point of jar. Dig out soil within circle until firm soil is reached, or height of eave of roof is 220 cm. Level excavation. Fill excavation 10 cm of concrete 1:3:4 (cement: sand: gravel); make it level compact it well. Floor Reinforcement Cut eight lengths of 7 m-long 3 mm galvanized wire. Bend wire ends to avoid injury. Mark middle of each wire. Tie eight wires together at marks as spokes in wheel. Make ring of 3 mm galvanized iron wire, 116 cm in diameter, tie it on spokes. Tie two 136 cm lengths of chicken wire overlaps of 10 cm to ring of wire. Place wires mesh on foundation. outlet pipe is made of 90 cm of 18 mm galvanized iron pipe onto elbow nipple are screwed to inner end, socket tap to outer end. Place pipe upon foundation. Fill Mold mold is then placed on foundation stuffed light, dry materials, e.g., sawdust, hay, or dung. Sand may be used. But since 3 m3 of sand weighs about 5 tons, mold made of canvas will burst unless most of sand is kept in buckets, stacked on layers of timbers separating rows of buckets (see Figure 33). Wall Reinforcement Chicken wire is wrapped tightly around stuffed mold while chicken wire lying under mold is bent up against side of mold. 16 wires sticking out from under mold are now tied on to ring of wire at top of mold spaced equally. end of roll of 3 mm wire is tied on to foundation wrapped tightly around mold as spiral spaced 20 cm from top of mold. External Plaster Plaster 1:3 (cement: sand) is smeared onto mold in thin layer. After couple of hours more plaster is applied to mold until plaster is 2 cm thick. While plaster cures 3 days, tap station is built. Internal Plaster Finish After three days, mold its contents are removed. jar is cleaned before plaster 1:3 is applied to internal side of jar in two layers, each layer being 1 cm thick. floor is made of 5 cm-thick plaster of 1:3. On same day, cement water are mixed Nil , steel trowel, pressed into moist plaster waterproofing. Place 2 concentric rings of plain sheet metal 10 cm high 60 cm diameter on top of jar. Fill space 1:3 plaster to form manhole lip. Place pipe overflow through lid. Cover manhole mesh to prevent insects debris entering jar. Ultra-Light-Duty Ferrocement Description Ultra-light-duty ferrocement is way to contain most water least cement steel, using no form, but also lowest safety factors durability, in tanks of 500-2000 gal (1.9-7.6?m3). It's appropriate choice there are fairly skilled, patient masons not enough money to buy more adequate amount of material. In non-industrialized nations there is great deal of interest in inexpensive water storage tanks. Ferrocement is one of most popular options. Some of these systems take amount of reinforcement materials right down to absolute minimum. Even at this, they are holding up decades in field, catastrophic failures are rare. absolute minimum construction 've seen was in Mexico, locals were building 2000 gal (7.6 m3) tanks armature of welded wire mesh covered chicken wire--nothing more. armature is so floppy that it has to be held still circular-shaped guy wires or strings. To be honest, 've no idea how they get plaster to stick to single thickness of chicken wire; this is well beyond my ability as mason. know they use some backing-- example, piece of plywood held by someone on opposite side, or plastic bags tied to outside. This technique requires quite bit of skill, or much of plaster will end up on ground. mix is about 3:1:1 sand:cement:lime. total thickness is 3/4" to 1-1/4". After this first coat dries (usually too fast, since it is just barely hanging there in breeze, since most masons in non-industrialized nations aren't tuned into wetting masonry to slow curing), another coat is added inside outside. Considering overly fast curing, abundance of undesirable cold joints ( cured cement meets fresh cement), likely leak points, minimal reinforcement, often minimal cement cover over steel, it is surprising these tanks hold water. That hundreds of them do, do so about twenty years before they start to leak, is testimony to fundamental robustness of ferrocement. Once they start to leak, it's not going to be easy to repair them, only to slow downhill slide (see photos at left). am intrigued by ecology of these tanks, very low use of materials they offer. these few refinements, think they could last perhaps twice as long: Proper curing is chronically lacking in masonry of non-industrialized nations. Diligent covering rags wrapping plastic, frequent wetting, especially on sunny side would greatly improve strength longevity of tank. Reused pallet wrap (giant, strong saran wrap, scavenged from receiving dock of some warehouse) is ultimate slow curing aid. Thicker mortar. failure mode seems to be corroding of chicken wire. Having at least 1 cm of mortar coverage over all steel would greatly extend life of tank. As practical matter, this can probably only be achieved by doing one or more extra coats of plaster inside out-- initial coats can only be so thick, as they aren't really attached to anything. These could be done rapidly unskilled labor, using soupy mix applied mason's brush. Extra reinforcement at bottom to contain higher pressure there reduce chance of leaks in this most inconvenient of locations. Use perhaps three turns of thick annealed wire, second layer of welded wire mesh, or one or two hoops of rebar around bottom 20% of tank. This would almost double pressure resistance little added cost. These refinements are incorporated in Plans Light-Duty Ferrocement, below. construction procedure is similar to that in Plans Heavy-Duty Ferrocement described in great detail below, except that there are two layers of reinforcement instead of several. If you are not skilled mason want to attempt one of these, use expanded metal lath instead of chicken wire, you will have fighting chance. Light-Duty Ferrocement Plans Plans from Intermediate Technology Development Group18 somewhat more reinforced, but still lightweight tank of 12,000 gal (46 m3), maximum size 'd make without rebar. They can be scaled to build tank sizes from 500-12,000 gal (2-46 m3). This system has lower safety factors durability than medium- or heavy-duty construction, is most suited to non-industrialized nations, money material is very tight. It requires fairly skilled masons. Approximately 4000 such tanks have been built in Kenya, to provide harvested rainwater drinking water at rural schools. Excavation If tank is to be used rainwater harvesting, edge of excavation circle should be at mid point of gable roof of house, 90 cm from house wall at least 300 cm below eave of roof. In any case, draw circle from midpoint of tank, radius of 285 cm. excavation should be at least 300 cm below eave of roof at least 15 cm deep, or until firm soil is reached. Make floor of excavation level. Welded Wire Mesh Floor Wall Two lengths of 560 cm are cut from roll of welded wire mesh (mesh, henceforth) tied together to form square sheet of 560 cm 560 cm. sheet is then cut into circle radius of 280?cm. length of 1740 cm is cut from roll of mesh tied into cylinder radius of 270 cm. vertical wires at bottom are bent to each side alternately. cylinder is then placed evenly on circular sheet tied to it tie wire. Foundation Concrete 1:3:4 is mixed placed in 7 cm-thick layer in excavation without moistening soil. mesh outlet pipe are placed on concrete. 6 cm-thick layer of concrete 1:3:4 is compacted on to first layer of concrete left rough surface. Wall Chicken wire is wrapped tightly around mesh, twisted tied on. 3 mm galvanized iron wire is wrapped tightly four times around chicken mesh at floor level from it continues as spiral to top of mesh it is again wrapped around four times. spacing of spiral is 5 cm at lower half of wall 10 cm at top half. Plastic sacks are hung against outer side of wall kept tight in place spiral of string starting from top. Mortar 1:3 is smeared against plastic sacks on their inner side. Next day, 2.5 cm layer of plaster is plastered onto smear floor finished Nil ( mixture of cement water consistency of porridge). sacks are removed outer wall is plastered 2.5 cm of plaster 1:3 sand: cement. Dome Erect formwork cover plastic sacks mesh. Bend vertical mesh ends in wall over mesh in dome. Lightly compact 5 cm plaster 1:3 onto dome while lifting mesh into middle of plaster. Use washbasin as form manhole. Make 20 cm 20 cm inlet holes. Cover finished dome plastic sacks weighed down by sand or soil. Do not walk on dome seven days, after formwork can be removed. Inlets, Overflow, Tap Build inlets install overflow pipe over tap-stand, can be closed door. Seal joint between dome wall. Medium-Duty Shaped Ferrocement Photos Many people have asked plans our 3500 gal (13?m3) urn-shaped ferrocement tank. These photos show its construction, how you can bend armature to get unique shapes in ferrocement. construction technique shown is applicable to building tanks from 1000-15,000 gal (3.8-5.7 m3), in industrialized non-industrialized countries. most accessible technique ferrocement in industrialized world is use of expanded metal lath over rebar framework. 've found this works best chicken wire on other side. minimum reinforcement is grid of 3/8" rebar, about foot on center both ways. Everything needs to be tied off really well tight, is very time-consuming process done wire pliers. There is certain technique to getting it tight doing it fast (see photos idea to get you started). somewhat skilled mason can plaster it by hand, pushing through chicken wire onto lath. After this structural coat dries, it generally needs at least one other coat on each side, followed by any color or sealer coats you wish to add. Tanks made by this technique often ?weep" due to unavoidably large number of cold joints. However, these small leaks usually seal up mineral deposits before long, in any case they are usually so small they don't even drip. similar technique is often used to make artificial rocks pools in zoos. inside of ?rocks" is often left unfinished; if you look in there you can see lath rebar. Again, it is amazing this construction lasts, but it does. Some of unusual features that worked well on this tank are: shape color ( neighbors like it so much more than we dared think, that wish 'd made it taller, so it would serve as hedge) water-harvesting wings that catch rain, allow about 300 gal (1 m3) of dirty house roof wash water to be stored separately, on top of tank many inlets outlets made from PVC sawn-in criss-crosses, none of leak hidden inlet pipe passes through tank floor roof overflow goes in wide, thin waterfall across several feet of wing (looks very cool) sloped floor drain sump make cleaning very easy reduced visual mass of tank due to partial burial Heavy-Duty Ferrocement Plans These are detailed plans constructing 30,000 gal (110 m3) tank, can be scaled from 3000 to ( help of engineer) 100,000 gal (11-380 m3). This technique has highest safety factors longevity. It is most suited to industrialized nation context tanks of greater than 30,000 gal in non-industrialized countries. Since all masonry can be hired out, in theory this kind of tank could be built even if you don't have any masonry experience at all. 'd say gamble in materials large tank seems too big to me to attempt without extensive prior construction experience. People who make ferrocement tanks living--especially large ones--quickly tired of all tedious labor have come up some innovations conserve huge amount of time improve results. main innovations are: thicker, stronger armature that works tanks up to 100,000 gal can support wet plaster applied from top down numerous time-saving details such as use of hog-ring pliers (manual pneumatic) in place of pliers wire plastering whole thing in one day to make totally cold-joint-free tank, using plaster mixer pump (or large crew doing it by hand) extra materials cost of heavy-duty ferrocement is considerable, but not only does this method save great deal of time; it makes stronger, more waterproof tank by eliminating cold joints. If you can afford extra materials in armature hiring crew to plaster it, this is by far preferred way to make ferrocement tank of 3000-100,000 gal capacity. We're going to describe tools materials needed, then describe in detail construction sequence this way of making tank. Read this through all way few times don't start your tank until unless it makes perfect sense. tank bigger than few thousand gallons is way too big of project to screw up. If you want to make big tank, but feel uneasy about following this procedure, suggest you make smaller one first to get familiar process. (See Figure 26, p. 73, Plumbing Options Multiple Tanks). Also, suggest you carefully read Appendix B, p. 91, Tank Loads Structural Considerations as well. Especially if you are building 30,000 gal or bigger tank, it is essential that you have good grasp of structural considerations before diving in. Note: This procedure is so geared to U.S. materials, methods, context, we've elected not to clog text metric conversions materials. Most of conversions can be found in Appendix , p .90. Tools In approximate order of appearance? Tape measures measure twice, cut once Water level leveling floor String marking radius, levels Level checking angle on drainpipe, floor, plumb on walls Flat shovel, pick site prep *Digging bar site prep, levering armature up to put dobies underneath PVC saw to cut drainpipe Diagonal cutters or mini-bolt cutters welded wire mesh *Hog-ring pliers hog rings37 * ?Willard" rebar cutter-bender, expensive but very handy. See if you can borrow one. If not, cutting, use hacksaw, angle grinder, or Skilsaw metal blade. bending, use next two items below ( are useful even if you do most bending on Willard). Rebar hickey bending rebar 30" length of 3/4" galvanized pipe handy bending rebar Tie wire swivel tool to manually tie rebar tie wire Linesman's pliers to tie off tie wire Tin snips to cut hardware cloth, lath Six- eight-foot step ladders to work on roof ceiling *Pneumatic hog-ring pliers (optional) To install thousands of wire ties necessary to hold armature together tight. Hog-ring pliers, /or pneumatic hog-ring guns, can be employed huge time savings over doing whole thing by hand wire. Pool trowels, one per finisher (other trowel types can be used if that's all you've got) Wood saw to cut roof braces to length *Air compressor (optional, or CO2 tanks to run air tools) Water under pressure, if possible (or ability to set up pump to create pressure) Rubber boots slab work *Concrete tamper getting voids out of slab *Plaster mixer, pump (usually comes crew of plasterers), or-- Cement mixer, shovels, buckets, wheelbarrow to mix plaster by hand Mason's brush applying color coat 5 gallon buckets Heavy rubber gloves * Tools denoted asterisk are optional. other tools are needed all ferrocement construction techniques. Materials quantities in Table 12 (above) are approximate. Concrete, especially is critical. Calculate amount your tank shape slab thickness using formulas in Appendix or our Tank Calculator.6 Always order 10-20% more concrete than you calculate that you will use. Notes on materials: Dobies to maintain spacing between floor rebar earth Poles to support ceiling: 4x4" or 3" round minimum large tanks Pallet wrap to wrap tank to slow moisture loss from plaster Concrete 1:2:3 cement: sand: gravel is good mix; or 6 sacks per cubic yard ordering by truck Plaster 1:3 cement: sand should be sufficient (Paul uses 1:2 in his tanks) Labor Design, site prep: Varies. Armature prep: Approximate times, assuming easy access, materials already on site, no learning curve delays, no design problems or big mistakes: 2000 gal tank: three days two people 5000 gal tank: four days two people 50,000 gal tank: three to four weeks four people 100,000 gal tank: two months six people Pouring floor concrete truck pumper is counted as one of above days. Plaster: mixer pump, one day By hand, up to 20,000 gal in one day eight people, two days larger tanks Then you wait week?. Color coat clean-up: Two work days separated by drying day Design Make detailed drawing of your tank try as much as possible to work out any design issues on paper. These instructions should enable handy person skilled help on plastering to make tank up to 30,000 gal in size. It can be scaled down to 5000 or 3000 gal tanks. Any smaller than that degree of overbuild is ridiculous--use medium-duty ferrocement construction. larger tanks (up to 100,000 gal), you'll want to engage engineer to test soil tank is going to be resting on, to specify spacing of rebar slab thickness. Site Prep Here's site prep checklist. Access is first order of business. If you can drive truck right up to tank site, have water under pressure power right there, that is ideal. If you can run plaster pump hose from closest vehicle access to tank site, that will save carrying heaviest material. If site is walk-in only, you can still do it, but you're going to have to carry everything, as well as mix apply plaster by hand (unless you are able to pump plaster, can be done 350-500 feet even uphill). If terrain permits, you can make temporary pressurized water system tank work site by pumping water to small, temporary tank higher up. If site is vegetated, you'll want to clear area few times bigger than tank, to provide clearance to work, store materials, mix plaster. If soil has high clay content, you'll want to lay down 6" of compacted road base or gravel to pour floor on. Grade Floor Most of these tanks have been built flat floor drain sump at one side. This is significantly easier to build than sloped floor, it is easy enough to sweep resulting puddles into sump during tank cleaning broom. (Check sidebar on page 112 experimental floor options that could save material, add strength, make cleaning marginally easier.) flat floor, you just cut flat space into earth to pour on. How evenly do you need to dig? tolerance tighter than 1/2" perfect is waste of time. Drain Now dig hole drain sump, trench drainpipe. drain sump should be few inches deeper than low point of floor, foot or two around. However thick slab is, excavation will be that much bigger all way around. See Drain, p. 58, more info complete specs drain pipe, including leak-prevention measures: It is critical that tank not leak drainpipe passes through, as there is no access to do repair. You want drainpipe to slope 2%. pipe at drain sump end should terminate in coupling, 45?, 90?, or straight coupling. (See Figures 40, 41, p 112, 113.) You're going to fill whole trench concrete, at least 3" around pipe on all sides, to about 6" past tank edge. You can stop concrete from flowing further by packing rocks around pipe. portion of pipe that is to be encased in concrete should be held securely up off trench floor. To discourage concrete from cracking, you can wrap pipe in cylinder of welded wire mesh. concrete must adhere perfectly to pipe good seal. If you've got at least 3" of strong concrete rebar containing pressure, you can put 1/2" thick ring of bentonite/ tar cold joint seal around pipe. This will expand great force if water touches it, make complete seal (or crack concrete if it is not as thick as specified). Just before pipe exits cistern it may be helpful to give it few turns of insulating pipe wrap so it can wiggle in grip of cistern not crack, if tank shifts under its great weight. backfill should be free of rocks that could break pipe if this happens. Floor Inside Wall: Welded Wire Mesh Lay strips of welded wire mesh (called simply ?mesh" henceforth) across entire area of floor, overlapping edges between strips one or two squares (6" to 12"), extending beyond perimeter of tank at least two squares (see Figure 39, next page). If you've gone conical or domed floor, you may need to cut shorter strips of mesh overlap them. All joints should be hog-ringed together so mesh sits somewhat flat. It will be strongest ( least work) longest strips that can negotiate shape. Now cut strip of full-height (7') mesh to length of circumference of tank, plus few feet. Stand this up to make cylindrical wall, jockey it into position in circumference line (6" in from perimeter stakes), hog-ringing it all along its bottom edge to mesh on floor. Now you've got pretty good indication of what final tank is going to look like. If you want to change its diameter or location, speak now or forever hold your peace! You'll also notice that you no longer have way to get in out of tank. Cut smallest door you can get through in mesh. door should start two squares (one foot) above ground be maybe two feet wide three feet high. Some slit polyethylene drip tubing can be placed over cut edges to reduce snagging scraping on body parts. Floor Wall: Rebar floor roof can be reinforced rebar in grid or radial hoops pattern (Figure 39). Because of different ways roofs floors are loaded, roofs are stronger radial rebars hoops, floors are stronger grid. If two systems cross at floor, there will be extra concentration of rebar ends at floor to wall joint, it is most sorely needed. This is way prefer to do it tank this size, but either pattern can work either roof or floor. (Note: If you make both floor roof radial, you can run rebars continuously from middle of floor to middle of roof, simplifying construction of small tanks.) radial hoops, bend rebars into long-footed ?L" shapes. Slide feet of Ls through bottom hole in mesh (so feet are on top of floor mesh verticals are outside wall mesh). Now tie them in place to wall mesh one double rebar tie, to keep them from flopping over. first two verticals should go on either side of door. rest go along vertical wires on mesh, every two, three or four squares, depending on size of tank. Every 2' (four squares) has proven to be enough tanks smaller than 20,000 gal, every 18" up to 30,000 gal, every foot 40,000-100,000 gal. feet of Ls should go to ring around drain sump, just few long enough to be bent cross under drain sump to ring over on other side. vertical pieces can just stick up however far they do. grid, preferred method one in figures, place rebars in grid, every foot or two, depending on tank diameter. ends should protrude beyond walls 6" to 2'; these get bent up 90? into plane of wall. If you do grid, some of these bent-up wild ends will be verticals go, others won't. If you can bend them bit to get them spaced evenly, that's advantage, but don't worry about it too much (Figure 39). This floor-to-wall joint (Figure 42, below) is advantage of grid is. It uses roughly same amount of material as radial pattern, but instead of ?extra" rebar density being in middle of floor (as is case radial pattern), it is at wall-to-floor joint, shear stress is greatest reinforcement is most needed. These extra rebar ends help keep walls from tearing outward from floor under pressure. Bend these wild grid ends up into plane of wall. If you've done grid, now you'll add verticals that have short-footed L shape. short foot of L should extend into plane of floor foot or two, be tied to one or more floor rebars. How high should ends go up? All that's left-- wild ends will get bent down to make roof. This is extra work of grid floor is: dealing these wild ends. It may be helpful to put up hoop of rebar at top of mesh to help hold them. Just make sure verticals end up on outside of mesh but inside hoop. horizontal wall rebars (hoops) should be bigger /or spaced more closely loads are greatest. At bottom, both hoop stress (from pressure pushing out) shear (from walls trying to push away from floor) are greatest. Figure 43 shows suggested hoop spacing different wall heights. first hoop is at very bottom. It catches all verticals bent-up floor ends whose job it is to contain. second hoop to be placed is one goes 1' up, at bottom edge of access door you are about to cut. All rebars are joined end to end should overlap at least 50 diameters (two feet 1/2", 18 inches 3/8" rebar) have three tight, double ties to hold them together. This can be fudged bit in non-critical places, but hoops are totally critical; they are under quite bit of tension stress. By way, if you are tempted to weld rebars together, forget it. Welding destroys strength of rebar (unless it is rare weldable type). Now add rest of hoops. Every hoop should be tied doubled wire tie at every crossing of vertical rebar. If you did radial floor, now is time to add floor circles. Radial or grid, every crossing of floor rebar--every crossing of rebar, period--should be securely hand-tied doubled wire tie. mesh should be wired to rebars all over, so that you step through puddle of concrete onto mesh it doesn't pull loose get pushed down into dirt, it will rust possibly crack your slab. Inlet, Outlet, Overflow Hardware Before second layer of mesh is put on is good time to add inlet, outlet, overflow fittings. These can be galvanized, PVC, or brass. If there is any chance you will be person who is going to have to replace fittings they rust out, suggest you use brass. Why build tank that could last 100 years fittings that are guaranteed to fail in 30? Brass fittings are expensive, but bargain compared to work of replacing rusted-out galvanized ones. You can weld (or solder, in case of brass) tangs sticking off of couplings to keep them from spinning in wall someone is trying to crank out rusted fitting pipe wrench (another reason to use brass). tangs get tied to rebar. alternative to welding tangs to give fittings ?tooth" is to use 45? bends or tees plug in them-- tee is like one big tooth. (See Figure 18, Drain Options, p. 61.) Wall Outer Welded Wire Mesh, First Layer of Lath Hardware Cloth Cut ten-foot lengths of mesh, hog-ring them to inner mesh. These pieces of mesh should be offset 3" up 3" to side from inner mesh, so two together make 3" square holes instead of 6" square holes. Why lengths just ten feet long? Since outer mesh is on outside of wall rebar, it is making circle that is about inch bigger in radius. Thus, longer sections, further out of sync it will get vertical rebars inner mesh. Ten feet seems to be longest that works keeping wires somewhat in sync. two layers of mesh should be hog-ringed to each other all over place. Push your hand. Do they separate? Hog-ring ?em. You can use short piece of rebar to pry pieces together joining. In 2' x 2' section between rebars, it is not unreasonable to have ten hog-rings. Those wings of excess floor mesh you've been tripping on this whole time? Now is time to bend them up out of way. You can cut off excess on corners, bending them up hog-ringing them to outside mesh. As mentioned before, more steel thicker plaster near bottom better. Add bottom rows of expanded metal lath (?lath" henceforth) inside hardware cloth on outside of wall. These will get buried few inches in concrete of floor help take shear force between walls floor. These two items get stapled pneumatic hog-ring gun if you've got fancy tool, or same old manual hog-rings if not. Lift Whole Thing Up Get Ready to Pour Get out your digging bar lever armature up onto dobies, starting at one side working your way towards other. (You can see dobies in action in photo above) How big should dobies be? Well, rebar should end up in middle or slightly towards bottom of slab greatest strength protection against corrosion. 'd go 2" dobies 5" slab, 3" 6" or 8" slab. If you are making small tank (10' diameter or less) want to spend extra time to save material, grade earth very perfectly use 1.5" dobies 4" slab. small dobies, take care they don't sink into earth too much (or use 2" dobies stomp them into earth 1/2".) dobies should be spaced such that you can walk on rebar without it bending so much that ties loosen--every couple to four feet, depending on stiffness of rebar. Check around that all is ready. Plug drain line at sump so it doesn't fill concrete, tape openings of outlets so threads don't foul splatters of concrete. Check that there is 3" of clearance all around drainpipe good seal concrete. Pull out any blown leaves or fallen dirt from around drain. Place securely wired scraps of rebar or dobies between floor rebar pipe to push it down against its supporting dobies, so pressure of inrushing concrete from hose cannot move it in any direction. Pour Floor easy, expensive way to do pour is to hire truck to mix bring concrete, pumper to spread it evenly over floor, finisher or two to smooth level it. In this case you just ask their strong mix (six 94 lb sacks of cement per cubic yard) pea gravel, so it can make it through pumper hose. hard way is to get bunch of your friends to mix cement by hand (or mixer), carry it in through that little door in wheelbarrows or buckets, finish it yourself. In this case you can use 1:2:3 cement: sand: gravel mix. 3/4" gravel will add more crack-resistance. If you've ever poured concrete, don't need to tell you that you want everything tidied up, all tools materials on hand, all hands on deck early start on pouring day. It is imperative that slab water tank be completed in one continuous pour, no cold joints. If it cracks, it's not just aesthetic issue; it is big leak at very bottom of your tank. truck, pumper, two finishers, you should be able to finish slab up to 20' across before concrete sets up too much, .e., half day. You might want to add few more helpers bigger-diameter slab. would not even attempt hand-mixed, hand-poured water tank slab any bigger than 6' across 4" thick without generously sized, proven crew that you are positive--based on past performance--can finish up before dark. 'd still have klieg lights on hand just in case?. If soil is dry, wet lightly before concrete goes on. As concrete is applied around edges, someone rubber boots needs to spooge it to outside several inches, as someone outside pushes it up three to several inches on outside of wall armature. ideal is to end up sort of triangular fillet of concrete on both sides of wall--see Figure 42, p. 113. This triangle will be encased wall plaster on both sides, providing much less crack- leak-prone joint to wall than simple butt joint. Of course, it's best to work from furthest reaches of inside back towards door. At critical places, such as around ( especially under) drain line, you can ensure void-free fill by filling from bottom up. If you shove hose down next to (well-anchored) pipe, concrete will boil up on both sides of it from bottom up, pushing air ahead of it. You can also push around it trowel. Tamp concrete into place concrete tamper to ensure that it is void-free. You can see one in photo on p. 115. floor slope can be judged by eye finished fairly rough, but draining tank may then leave puddles. This will be less work to make, more work to clean. If, on other hand, idea of easily-made yet wobbly floor offends thee, enlist aid of screed setup designed by someone who has experience making slabs to get slope just right (see sidebar at right.) Once floor has set up hard enough to kneel on atop small piece of plywood without sinking in, it is time to smooth out top surface. Impress on your helpers that you do not want mirror-smooth, shuffleboard-court type finish it seems you would want easy cleaning. You want to leave enough ?tooth" that Thoroughseal coat sticks. If you want smooth finish ( isn't as crucial as slope cleaning ease, since you'll be sweeping it anyway), you'll have to try make it in sealer coats. drain sump is good thing to have smooth, as this is all gunk will congregate resist going down drain. Make sure no part of sump is below spill point of drain. After you've convinced yourself pour has been finished perfectly, clean tools go to sleep. next morning you can securely cap drain, flood slab (up to top of little ridge of concrete you pushed up around perimeter) forget about it day or three while you pay attention to your friends family. Stop by once in while spray down outside edge of slab, especially on south side. You can slow drying by putting wet blankets over concrete plastic tarps over that. slower it dries, less likely it is to crack. You should keep it sopping wet couple of days damp week or more. Roof, Cool Shapes, Ladder Now that rebars are held solidly at bottom in cured concrete, you can bend down wild ends of vertical rebars to form roof. How domed of roof should you make? more curved it is, harder it is to make (because of awkward fit of mesh to compound curve). high, steeply curved dome makes stronger roof. However, this advantage is outweighed by large increase in water pressure on lower wall relative pittance in increased storage capacity. advocate fairly flat dome, rising about 1/10th of its diameter. rings on radial pattern roof contain strong outward forces generated as people walk on it. That is structural advantage of radial pattern roof. On big roof, it is nice touch to make top wall hoop rebar-size fatter, or add another near it good measure. (Remember, all hoops go outside verticals, to contain them.) Rebars joined end-to-end should be overlapped at least 50 diameters, especially rings hoops, are under tension. (See Figure 44, p.115). What curve should you use? choice is not critical, unless you are making flat dome, in case strongest curve overall is section of circle, that is, constant curve. If curve is variable, instance, more curved near wall less curved in middle ( is what you'll get if you just pull rebar down your hand), less curved section will be less able to resist point loads from people walking on it. If you want ?wings" or lip on side of tank so that it can harvest water from its own roof, now is time to add them. Wings will require another hoop, held in place by short verticals or ends of roof grid members that extend beyond edge. There is little load on modest-sized (under 2') wings, so they can be lightly reinforced. You can make them thin, fat lip of lath to strengthen outside edge. vertical rebars, are spaced evenly around circumference, can be tweaked over to line up roof grid lines, if you're doing grid roof. As it is under least pressure, roof isn't so critical. If grid is bit--or lot--wank- -doodle, it will still be fine. This is time to attach access hatch, if you've had one made, or form one if you're making it yourself. access hatch on edge has advantage that it can be located over integrated ladder in wall, you'll have easier time getting in to plaster inside without thrashing fresh plaster on roof. If you telescope it up, as shown in Figure 41, p. 112, it gives you point to attach your inlet above high water level without snaking pipe over your lovely roof. (Or, if you really care about aesthetics, pass inlet through low on wall of tank telescope up above maximum water level inside tank, measure can help against freezing, too.) access hatch at high point, in middle (or telescoped up), has advantage that it can potentially enable quite bit more water to be stored above walls but below roof. If you want to make rock-shaped tank, this is time to get creative. In order to resist water pressure, all parts of walls that have four feet or more of water pressing on them need to be circular. That is, bottom four feet of eight-foot tank, bottom six feet of ten-foot tank. closer you get to top, lower water pressure more wild you can get shape, without inviting structural problems. Compound curves are inherently strong, can start lower on tank wall, changes in diameter (as in urn-shaped tanks described previously) are still circular, thus don't compromise strength. stress on roof is low. You can make it all bumpy asymmetrical, starting at different heights, it will still be plenty strong, as long as there are not big flat sections (see photo, p. 38). pressure at bottom of tank is proportional to height of highest water level, regardless of how much volume of water is up there. This is species of leverage. If you make hollow ?rock" narrow spike sticking up twenty feet, even if spike is only few inches around, if thing can fill water it will add twenty feet of pressure to tank. This might well blow apart even massive lower structure (see Figure 32, p. 91). Conversely, fanning out to wider diameter above (as in urn) adds no more pressure below. This is why clay urns are urn-shaped; flare at top adds volume without increasing tension on clay at bottom. regular domed, radial rebar roof, you just give wall rebars concentrated bend at top of wall, directly down almost 90?, pipe rebar hickey, until they are in plane of dome edge. From there you can give them gentle, distributed bend into rest of dome curve. Once you've got rebar all tied off, drape strips of mesh over whole top, usual 1 to 2-square overlap. These need to be hog-ringed they are sticking up above rebar. If dome is very curved, you may need to clip mesh in places (or twist individual wires into ?Z"s to shorten them) to get mesh to conform to curve. ceiling welded-wire mesh is installed in similar fashion, except that it is made of shorter (ten-foot) strips, tightly rolled fed through side door. These must be well hog-ringed, as they may find themselves supporting big slug of heavy, wet plaster mason's foot. If you are going to make integrated ladder, this is time to put it in. specs, see Service Access, p. 56. If you want, you can add pole or permanent ladder in middle. If ladder is steel, you can bolt it to anchors in floor slab, let it slide on inside of hatch during construction, then cut it to length bolt or weld it to hatch after tank has cured. If you use steel pole, 2" is plenty. It should be bolted to floor, covered hardware cloth plastered to keep it from corroding. Lath Hardware Cloth Lath goes on inside surface of whole thing now. Use 2.5 lb/yd2 galvanized lath, cups facing up, edges overlapping 2". Lath goes on inside to catch plaster you apply from outside. Plaster easily passes through 1/2" hardware cloth, you are now going to skin entire outside. 1/2" chicken wire is cheaper can also be used, but hardware cloth is stronger smoother to trowel over. (Chicken wire or lightest-weight expanded metal lath can conform to compound curves are materials of choice any small, curvy details you've incorporated.) Both lath hardware cloth can be attached pneumatic hog-ring gun, if you're so lucky as to have one. Both should be checked all over by pushing your hand, hog-ringed really tight. Twenty hog-rings in 2' x 2' square are not excessive. lath on inside of ceiling should be especially tight. If it pushes in as cement is going on, it's not going to be possible to pull it back once it's filled cement. Plaster Prep: Roof Supports, Seal Door plaster doesn't contribute much to strength of armature until it has dried several hours. Since tank is plastered from top down, armature itself must be made stiff strong enough to support much of weight of few workers tons of wet plaster, help of numerous supports under roof. tanks bigger than 10,000 gal, mixture of 4 x 4s 2 x 4s will do as roof supports. smaller tanks, 2 x 4s or 2 x 6s will work. Undressed green poles also work fine. If you drive nail through lath into end of poles, that will keep them from falling over. If supports lean ever so slightly to one side they will be easier to knock out afterwards. Seal off temporary access door now, patching over it mesh, lath, hardware cloth. Be sure to overlap everything generously. Clean off slab (so you can scoop up reuse plaster that lands on it). Clean any debris out of tangle of rebar mesh at floor-to-wall joint compressed air or water. It is crucial that this area be clean leak-free joint. Check that all is tied off perfectly, have bulk sand cement delivered, arrange plenty of help. If you go plaster mixer route, you'll want: big plaster mixer plaster pump one semi-skilled person to make mix one person to direct hose end two skilled plasterers to trowel out plaster as it goes on one laborer to move hoses, clean tools, etc. These figures include whatever workers come equipment. As mentioned before, you'll want to start early. good crew, you can mostly just watch them go, be finished before you get too hungry. example, five-person crew recently finished 10,000 gal tank in 5 hours. If you are manually mixing plaster, you'll want: two semi-skilled people to mix plaster one or two laborers to deliver it to finishers two to four skilled finishers to apply finish plaster as it goes on one laborer to clean tools, etc. It is all but impossible to finish entire big tank manually in day. example, good crew of four was able to do 45,000 gal tank in two long, hard days. mixer or by hand, plaster is really rich: one part cement to two or three parts sand. 1:3 is OK if plaster sticks well enough. Plaster Whole Tank Sequence your work to avoid disturbing fresh plaster. If you start from bottom work up, you'll be leaning ladders against wet plaster. this reason, preferred sequence is to start at top work down. Do area around access hole first, it will be better cured you've finished phase have to go in or out of it. If you are using plaster pump First spray inside, from top to bottom, very, very light coat (1/8"). Plaster comes out pump hose sort of like popping popcorn. If hose is held back ways, it will result in lighter coverage as spray covers wider area. Let it cure half hour. This coat keeps heavy plaster coat that is coming next from pouring through inside. Now spray outside to thickness that fills armature completely to voidless condition leaves generous, protecting cover of 1/2" to 3/4" over it. After you've covered entire outside troweled it to its final finish, take break, eat some food while plaster is setting up bit, before heading inside. If access is in middle, run plank from step ladder outside tank to well-supported lip of access hatch. Run plaster hose along plank. It's going to be dark inside now, hot, from chemical reaction of cement. You may need lights to do good job. You could run extension through inlet. If plaster has rained onto floor from outside, you can use it fillet between floor walls. Give inside medium coat (3/8" to 5/8" cover over armature) from top to bottom, troweled to final finish. If you are manually mixing plaster, plaster is applied from top to bottom, as plaster pump. hand mixing, it is better to apply finish plaster on inside outside in same place at same time, one finisher on inside one on outside. After all plastering is done, clean tools get some sleep. Keep It Wet As soon as plaster gets hard, start wetting tank down. One tank maker in Hawaii wraps his tanks in pallet wrap. Since water then can't escape tank, it needs little attention. Plug drain flood cured floor water to keep it humid, you'll get really nice, slow cure. Alternatively, you can just keep wetting plaster regularly, blankets tarps to store water keep it from evaporating rapidly. Some people have rigged automatic sprinkler setups. After three days, you can remove supports from inside, clipping protruding nails off held them in place. holes supports were will need patching. Any remaining drips that landed on floor can be chipped off now. Keep tank saturated wet three days damp week or two, especially on sunny side. Color Seal It week later, after cement has cured fully, you can add color coat to outside. color goes into Thoroughseal. (Thoroughseal is cementatious sealer. Thoroughseal ?foundation coat" is cheaper , being grey instead of white, makes more attractive earth tones). At same time inside can be sealed two coats of Thoroughseal. You may be tempted to use 1:1 sand cement instead of Thoroughseal. It is certainly cheaper, but not as durable. On related note, silica sand tends to pop out of wall. Whatever sealer you use inside, you should confirm that it is safe potable water.20 Adding some color to first interior seal coat (only) makes it easier to confirm coverage of both coats inside dark tank. Thoroughseal should be about consistency of pancake batter. It's applied big mason's brush. color is place you can get really creative. If you are particular about color, try it on big swatches, keeping very careful track of measurements procedure. (Davis concrete pigments make best plaster colors.) All sorts of things affect how color turns out; sand, cement, amount of water, curing conditions? suggest you forget about getting uniform color, try instead interesting patina. Besides mixing color into cement, you can also sprinkle it onto surface work it in to get more mottled appearance. Note that it must be stirred in well--if there are isolated clumps of concentrated color, they are likely to degrade rapidly. Bear in mind that colors lighten dramatically over time. Red, some reason, seems more durable than other colors, so things tend to turn out more pink than intended. Once color is done, you can backfill around tank do finish grading. ground around tank should be mounded so that runoff will head away from tank. Fill It new ferrocement tank should be kept mostly full month or two final curing. It is normal new tank to weep slight amounts of water in places (often on sunny side, cure was too fast). Don't be alarmed--usually this seals up. As cement swimming pool, it is best tank if you never let it dry out completely. There you go--you've got lifetime water tank! Endnotes Updates & clickable links: oasisdesign.net/water/storage 1 Principles of Ecological Design Art Ludwig. Oasis Design. Principles redesigning our way of life to live better less resource use. See description on inside back cover free online summary at www.oasisdesign.net/design/principles.htm. 2 Create Oasis Greywater Art Ludwig. Oasis Design. See inside back cover. There is free online summary of common greywater mistakes preferred practices at www.oasisdesign.net/greywater/misinfo. 3 Rainwater Harvesting Runoff Management Art Ludwig. Oasis Design. Forthcoming--see description on inside back cover www.oasisdesign.net/water/rainharvesting 4 Water Quality Testing Procedures Information Packet Art Ludwig. Oasis Design. set of downloadable files will help you learn water testing techniques interpret results. See inside back cover, also www.oasisdesign.net/water/quality/coliform.htm. 5 American Journal of Public Health, Robert D. Morris. 1992. 6 Water Storage Extras Oasis Design. Includes Water Tank Calculator, Research notes on materials leaching, bacterial regrowth, disinfection by-products, permeation, water system component spreadsheet. See inside back cover www.oasisdesign.net/water/storage. 7 NRDC's March 1999 petition to FDA Includes report on results of their four-year study of bottled water industry, including bacterial chemical contamination problems. petition report find major gaps in bottled water regulation conclude that bottled water is not necessarily safer than tap water. See www.nrdc.org/water/drinking/bw/bwinx.asp. 8 National Testing Laboratories, Ltd. Network Phone 440-449-2525 or 800-458-3330, Fax 440-449-8585, E-mail: ntlsales@ntllabs.com. www.ntllabs.com. Offer $130 water test 75 parameters. As detection limits are disappointingly high you are unlikely to find anything unless water is really bad, but price can't be beat. 9 Builder's Greywater Guide Art Ludwig. Oasis Design. www.oasisdesign.net/greywater. Figure 7, p. 43: How Treatment Capacity Contamination Plumes Change Location of Wastewater Application. 10Ponds--Planning, Design, Construction USDA Natural Resources Conservation Service (NRCS), Agriculture Handbook 590. Call your local Natural Resources Conservation Service office to get copy. 11Building Pond Land Owner Resource Centre. P.O. Box 599, 5524 Dickinson Street, Manotick, Ontario K4M 1A5. Phone 613-692-2390 or 1-800-387-5304, Fax 613-692-2806, Product Ordering 1-888-571-INFO (4636), info@lrconline.com, www.lrconline.com. 12Pond Construction: Some Practical Considerations Virginia Cooperative Extension, Fisheries Wildlife, 1997 PUBLICATION 420-011. www.ext.vt.edu/pubs/fisheries/420-011/420-011.html. 13Local weather station data. Try searching web ?evapotranspiration" ?weather station" name of your area. Here's example of what you're looking : wwwcimis.water.ca.gov/cimis 14Solutions to Common Fish Pond Problems L. . Helfrich, Extension Specialist. Fisheries Virginia Tech. Publication Number 420-019, 1999. 15Natural Swimming Pools/Ponds - Total Guide. Total Habitat.www.totalhabitat.com/P&P.html. Designers & Builders of Natural Swimming Pools/Ponds. 16A Handbook of Gravity Flow Water Systems Thomas D. Jordan, Jr. Intermediate Technology Development Group. 1980. Portions of Sizing Water Tanks section comments on stone tank shape are paraphrased from this work. stone tanks they suggest octagonal tanks diameters less than 2.5 m, hexagonal shape tanks of at least 2 m square tanks small capacities. Includes procedures welding HDPE water lines. 17Effects of Water Age on Distribution System Water Quality American Water Works Association. Figure adapted by permission. 18Rainwater Catchment Systems Domestic Supply John Gould Erik Nissen-Petersen. Intermediate Technology Publications, 1999. Tank sizing figure adapted by permission. 19Water Distribution Systems Handbook Larry W. Mays. American Water Works Association, 1999. 20National Sanitation Foundation Searchable database of NSF 61 certified materials components: www.nsf.org/Certified/PwsComponents 21Paul Kemnitzer, Hollister Ranch 51, Gaviota, CA 93117. Tel 805 451-5153. Ferrocement pioneer, builder of quality ferrocement water tanks, homes structures in Southern California since 1982. Tanks from 3000-100,000 gal (11-380 m3), cylindrical or boulder-shaped, in natural colors. 22Pacific Gunite, Box 421, Mountain View, HI 96771. 808-968-6059, Fax 808-968-8668, www.ferrotanks.com. Cylindrical tanks from 1000-50,000+ gal. 23Report of New South Wales Chief Health Officer, 1997 www.health.nsw.gov.au/public-health/chorep97/env_watalum.htm. Aluminum Toxicity: Issues Insights www.bayeralbumin.com/web_docs/WP_Aluminum%20Toxicity.pdf 24Maritime Teak Deck Caulk 25Water Bladders in Culverts Earthwrights Designs. 505 986-1719, e-mail: ezentrix@aol.com. suggest you avail yourself of Earthwright's experience if you want one of these. They use aluminized steel culverts 30 mil PVC inside geotextile, or PP bladders. Cost is about $1/gal installed, capacity 10-50k gal. There is limited access cleaning. First ones installed in 2002. See www.waterstructures.com other storage bladder examples. 26Zodiac above ground pools www.zodiacpools.com 27Maruata en el Cruce de Caminos Art Ludwig. Oasis Design. Ecological systems designs indigenous community in Mexico, including water supply sanitation. See www.oasisdesign.net/design/examples/maruata/book.htm. 28Oxidation of Iron Manganese www.fcs.uga.edu/pubs/PDF/HACE-858-11.pdf. Iron manganese dissolve more readily deep underground, in absence of oxygen. As water is pumped to surface exposed to oxygen, process will reverse dissolved iron manganese will precipitate out of water forming colored sediment. Iron sediment is reddish brown or orange; manganese sediment is black or dark grey. See also www.healthgoods.com/Education/Healthy_Home_Information/Water_Quality/iron_manganese.htm. 29Non-modulating Float Valve CLA-VAL Automatic Control Valves. P.O. Box 1325, Newport Beach, CA 92659. 800-942-6326, Fax: (949) 548-5441. www.cla-val.com. Highly reliable, but expensive. 1/2" valve costs $450 supplies 19 gpm; enough most systems. Rebuild kit is $94. 30Watermaster 1016 Cliff Drive #321, Santa Barbara, CA 93109. 805-966-9981, Fax 805-705-5813, usawatermaster@juno.com. Source ozonators, water treatment consulting, equipment selection, installation. 31Information on sand filters See www.oasisdesign.net/water/treatment/slowsandfilter.htm. 32Tank Talk Newsletter Tank Industry Consultants. Excellent information on freezing in several past issues of this newsletter. It is geared towards large municipal tanks but much of information transfers. www.tankindustry.com/tanktalk.html 33National Fire Protection Association States sprinklers "reduce chances of dying in fire average property loss by one-half to two-thirds compared to sprinklers are not present. NFPA has no record of fire killing more than two people in completely sprinklered public assembly, educational, institutional or residential building..." 34Surface Water Treatment Rule US Environmental Protection Agency www.epa.gov/ogwdw000/smallsys/ndwac/surface.html. 35National Drinking Water Clearinghouse Skilled help small communities to run their water systems. 800-624-8301, www.nesc.wvu.edu/ndwc. 36Branched Drain Greywater Systems Art Ludwig. Oasis Design. Design, construction use of ?branched drain" greywater systems: simple design to achieve automated, reliable subsurface irrigation without pump, filter, valves or surge tank, using all off- -shelf components. See inside back cover www.oasisdesign.net/greywater/brancheddrain. 37Republic Fastener Products Corp. 1827 Waterview Drive, Great Falls, SC 29055. 800-386-1949. www.republicfastenerprod.com. Provides 3/4" 14 gauge steel hog-rings X2RP425 used all manual hog-ringing pliers from same supplier.


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