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Needed Improvements to the International Plumbing Code Appendix C: Gray Water Recycling Systems

See also UPC&CPC improvements for more general comments on gray water laws.

Based on 2000 IPC, appendix c, page 101:

c101.1 Differentiate between allowable uses for treated and untreated gray water. As it stands, reuse for toilet flushing is allowed with disinfection only, which may not be satisfactory if BOD remains high ° toilet tanks may become foul and anaerobic with stored, putrefying water. Treated gray water could be reused for other non-potable uses besides those listed, laundry for example.

Irrigation should be specifically allowed, not just as an exception.

c101.2 Expand definition to include all domestic wastewater other than toilet water. Exclusion of kitchen sink water leaves this particular wastewater flow in awkward limbo in facilities which have a gray water system and composting toilets. Instead, give performance requirements for dealing with high SS, BOD water.

c101.4 Reservoir. The reservoir should be optional, as storing gray water is not required for all system types and is undesirable. The not less than 50 gallons and not more than 72 hours retention requirements are potentially at odds with each other. 24 hours maximum retention is a better design goal, with the tank size left up to the designer.

c101.6 Disinfection. Disinfection should not be required for irrigation reuse.

c101.7 Makeup water. Should be optional depending on reuse. Toilet flushing requires makeup water for public health, irrigation does not.

c101.8 Overflow. Overflow pipe should be the same size or greater than the influent pipe. Allow possibility of connecting to alternate overflow as an exception, in order that facilities with composting toilets and gray water systems have the option of adding redundancy and safety features to these systems instead of a sewer hookup or septic system, or that if a septic system is required it may be downsized.

Excerpts from 2006 IPC

Copyright, 2006, International Code Council, excerpted from

Gray Water (Definition): Waste discharged from lavatories, bathtubs, showers, clothes washers, and laundry trays.

IPC 2006, Section 301.3 Connections to drainage system.

All plumbing fixtures, drains, appurtenances and appliances used to receive or discharge liquid wastes or sewage shall be directly connected to the sanitary drainage system of the building or premises, in accordance with the requirements of this code. This section shall not be construed to prevent indirect waste systems required by Chapter 8.

Exception: Bathtubs, showers, lavatories, clothes washers and laundry trays shall not be required to discharge to the sanitary drainage system where such fixtures discharge to an approved gray water system for flushing of water closets and urinals or for subsurface landscape irrigation.

IPC 2006, Appendix C, C101.1 Scope:

The provisions of this appendix shall govern the materials, design, construction and installation of gray water systems for flushing of water closets and urinals and for subsurface irrigation.

¹For purposes of this discussion, tertiary treatment shall result in water that is adequately oxidized, clarified, coagulated, filtered, and disinfected so that at some location in the treatment process, the seven day median number of total coliform bacteria in daily samples does not exceed two and two-tenths per one hundred milliliters, and the number of total coliform bacteria does not exceed twenty-three per one hundred milliliters in any sample. The water shall be filtered so that the daily average turbidity does not exceed two turbidity units upstream from the disinfection process.

Note that the Plan Review and Field Inspection guidance only applies to the provision granted in the IPC for collection of gray water from lavatories, bathtubs, showers, clothes washers, and laundry trays for use in flushing of water closets and urinals.

1. Confirm that the collection reservoir is designed to be constructed of durable, nonabsorbent, and corrosion-resistant materials. The reservoir shall be a closed and gas-tight vessel. Access openings shall be provided to allow inspection and cleaning of the reservoir interior.
2. Confirm that the distribution piping materials meets one of the standards listed in IPC 2006 Table 605.4.
3. Confirm that the gray water entering the reservoir will pass through an approved filter such as a media, sand, or diatomaceous earth.
4. Confirm that a full-open valve will be installed downstream of the last fixture connection to the gray water discharge pipe before entering the required filter.
5. Confirm that the collection reservoir design will meet the daily flushing requirements of the fixtures, have a maximum retention time less than 72 hours, and be sized to a minimum 50-gallon capacity.
6. Check that the collection reservoir is equipped with an overflow pipe having the same or larger diameter as the gray water influent pipe. Check that the drain is located at the lowest point of the collection reservoir and is the same diameter as the overflow pipe. Both the overflow pipe and the drain shall be directly connected to the sanitary drainage system.
7. Check that the collection reservoir is equipped with a vent sized in accordance with IPC 2006, Chapter 9, and based on the diameter of the reservoir influent pipe.

Field Inspection

1. Confirm that the collection reservoir and distribution piping meets the design criteria.
2. Confirm the gray water is disinfected by an approved method that employs one or more disinfectants such as chlorine, iodine, or ozone. Confirm the gray water is dyed blue or green with a food-grade vegetable dye.
3. Confirm the distribution piping and reservoirs are identified as containing nonpotable water.