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Oasis Design Updates & Errata

On this page:

Greywater book updates

Greywater links (complete)

AGWA systems out of business

Due to pressing needs from another family business, AGWA systems has ceased production. As AGWA was the best supplier for large scale automated systems, this leaves a huge void which someone will hopefully fill soon. The Earthstar, which was a partial substitute for a while is no longer available either. (Please Email us if you've found a substitute.)

Clarification of new construction/remodeling vs. retrofit realities

If you're dealing with new construction or remodeling, it is a totally different situation than a retrofit. Generally, with a retrofit, your only problem is getting it to work; you're about as likely to have to deal with regulatory trouble as you are to be struck by lightening. With new construction or remodeling, you are likely to have so much regulatory trouble that you may never get to the point of worrying about making it work, and if you do, your task will be greatly complicated by absurd requirements. Oasis greywater-book addresses the retrofit reality, and the  Builder's GW Guide-book is a supplement which addresses the regulatory issue. For a quick summary, open this link:  Builder's action summary.

System name changes, additions & deletions

Some names were changed to make them more descriptive…

Drain out back->Branched drain to mulch basins
Hard plumbing to mini-leachfields->Split drain to mulch basins or mini-leachfields
Enhanced drain out back->Movable drain to mulch basins

Leachlines under raised beds was deleted, as there are very few contexts in which it is appropriate, and having it in the book seemed to encourage people to use it where it was not appropriate. Most of the info on it can now be found in "greywater mistakes."

Settling tank an leachfields was consolidated with plants over the septic tank leachfield.

A new system, the Multi-mode greywater tank was added in the 12th printing of Create an Oasis.

Branched Drain to Mini-Leachfields are working well in the field

The "Branched Drain" system which was squeezed into Create an Oasis 6th printing at the last minute and described at some length in the Builder's Guide 2nd printing is my current favorite system. Installation requires a sobering amount of skill, especially with minimal slope, but they are holding up well to incredible abuse in the field. I installed the first known permitted system in Santa Barbara as part of a greywater test for the state of California. This system featured a "dipping bucket" with a magnetic counter to record the flow of water; about the only way to measure intermittent flow at atmospheric pressure. The irrigated area was only 1/4 per foot slope from the house; this doubled the time for the distribution plumbing.

I've also put in a small test system for a kitchen in the Yucatan, and the person who put this in went on to do an entire 3 bath house. These systems used straight thin wall pvc tees in place of ABS double ells. Cement was used around the pipes to encourage them to remain exactly level at points where the fitting was supported only on two of three sides, which occurs where the flow splits inside a 5 gallon bucket which was also the emitter. I've not yet gotten feedback on how this worked over time.

If you have any information on how this system works with heavy clay soil, hard freezes, or lots of kitchen grease, please  Email us .

There are two important variations not in any book:

Branched Drain to Mulch Basins

The best performing variation of this system for warm climates (and provided subsurface disposal is not required) is terminate each outlet 6" above the level of mulch in a mulch-filled basin. This requires more slope than mini-leachfields.

Branched Drain to Box Troughs in a Greenhouse

This design has not been tried, but promises automated, reliable distribution of effluent for year round treatment in cold climates, without pumps or filters. This system should be quite frost resistant. If you're interested in trying it, contact the office for a drawing.

Branched Drain to Mini Leachfields Surge capacity

Surge capacity in subsurface chambers should be calculated; you'll need more than you think. The short term contribution of soil infiltration can be ignored for all but highest perk soils. Consider the volume below the spill point of the inlet pipe only; the balance is unavailable as the water will simply back out the chamber and go to the lowest chamber. To get more surge capacity, use 5 gallon pots or buckets, or 15 gallon HDPE drums cut in half lengthwise. Also, surround chambers with mulch in a larger basin.

New materials for drumless laundry

The cleanest installation for the drumless laundry uses ALL 1" spa flex, replacing the black hose on the back of the machine. The configuration remains the same as shown in Create an Oasis.


We're pretty conservative about the info in the books, and there have been mercifully few heinous mistakes and errors:

Incorrect formula for estimating ET, page 25 of first printing Builder's Greywater Guides

The correct formula is:
ID=ET x PF x IA x 0.62

Builder's Guide 8th printing Index

Is missing the listings between I and S. You can read the complete Builder's Greywater Guide Index here.

Key to editions (approximate)

Oasis Greywater Information

A booklet superseded by Create an Oasis with Greywater in 1994 or so. Nothing is really wrong with the info in here, but there is so much more in Create an Oasis that you really should get a copy of the latter.

Create an Oasis with Grey Water, 4th ed. (book)

The printing number is near the bottom of the inside front cover.

1st printing is somewhat dated. 2nd-9th printings all have minor changes and additions. Printings 7-9 are nearly identical. Somehow we messed up on the printing numbers when we switched to Poor Richard's press; the printings labeled 5 and six are really printings 10 and 11. There are minor improvements in every edition between 10 and 15.

17th printing incorporates Arizona and New Mexico greywater law considerations, septic tank and eco chambers system replaced by septic tank and infiltrators system.


Oasis greywater-book


5th edition of Create an Oasis with Greywater; combines Create an Oasis and Branched drain greywater systems.


Builder's GW Guide-book

Originally loose sheets in the Builders' Greywater Info Toolkit, then much more material added to make the Building Professional's Greywater Guide, then basically just a name change to the current format. Minor improvements and additions from printing 1 to 8.

9th printing has four pages of new information including new information on Treatment vs application depth-pdf (jpeg graphic, 300k), and new legal information.

10th printing incorporates Arizona and New Mexico greywater laws, suggested improvements and considerations.

Branched drain greywater systems

The printing number is near the bottom of the inside front cover. All printings have minor improvements each edition.

5th printing incorporates Arizona and New Mexico greywater law considerations.