California Greywater Code

After many years of illegal graywater re-use by Californians, the code was substantially re-written.

Unfortunately many sections of the code encourage inefficient (i.e. wasteful) practices, and actively discourage best management practices. I will explain why after listing the major points of the code.

Rather than repeat the whole code here (it is 12 pages long!), here is the link:

January 27, 2010 (2007 CPC, Title 24, Part 5, Chapter 16A, Part I – Nonpotable Water Reuse Systems)

The following is a collection of excerpts that summarize the code.

Keep in mind “a city, county, or city and county or other local government may,after a public hearing and enactment of an ordinance or resolution, further restrict or prohibit the use of graywater systems. For additional information, see Health and Safety Code Section 18941.7.”

General definitions:

“Graywater” includes but is not limited to wastewater from bathtubs, showers, bathroom washbasins, clothes washing machines, and laundry tubs, but does not include wastewater from kitchen sinks or dishwashers.

Mulch Basin. A type of irrigation or disposal field filled with mulch or other approved permeable material of sufficient depth, length and width to prevent ponding or runoff. A mulch basin may include a basin around a
tree, a trough along a row of plants or other shapes necessary for irrigation or disposal.

Irrigation Field. An intended destination for graywater in the receiving landscape including but not limited to a drip irrigation system, mulch basin, or other approved method of dispersal for irrigation purposes.

Requirement for 2” covering

In general, any irrigation system must avoid graywater contact by being covered with 2” of material:

(G) Graywater shall not be used in spray irrigation, allowed to pond or runoff and shall not be discharged directly into or reach any storm sewer system or any surface body of water.

(H) Human contact with graywater or the soil irrigated by graywater shall be minimized and avoided, except as required to maintain the graywater system. The discharge point of any graywater irrigation or disposal field shall be covered by at least (2) inches (51 mm) of mulch, rock, or soil, or a solid shield to minimize the possibility of human contact.

(I) Graywater shall not be used to irrigate root crops or edible parts of food crops that touch the soil.

The code describes three types of systems:

  • Clothes Washer System. A graywater system utilizing only a single domestic clothes washing machine in a one- or two-family dwelling.This method cannot use a secondary pump and relies either on the washing machine pump or gravity to irrigate the garden areas.The amount of water from the washing machine is considered to be 15 gallons per person per day, e.g. 60 gallons per day for a 4 person household.

    A construction permit is not required for the Clothes Washer System A construction permit shall not be required for a clothes washer system which does not require cutting of the existing plumbing piping provided it is in compliance with Section 1603A.1.1.

  • Simple System. A graywater system serving a one- or two-family dwelling with a discharge of 250 gallons (947 L) per day or less. Simple systems exceed a clothes washer system.A construction permit is required for a simple system.
  • Complex System. Graywater systems that discharge over 250 gallons (947L) per day.A construction permit is required for a complex system.

Construction Permits

  • 1603A.0 Permit.A written construction permit shall be obtained from the Enforcing Agency prior to the erection, construction, reconstruction, installation, relocation or alteration of any graywater system that requires a permit.No construction permit for any graywater system shall be issued until a plot plan with appropriate data satisfactory to the Enforcing Agency has been submitted and approved. When there is insufficient lot area or inappropriate soil conditions to prevent the ponding or runoff of the graywater, as determined by the Enforcing Agency, no graywater system shall be allowed.
  • 1604A.0 Drawings and Specifications. Graywater systems for which a construction permit is required may be subject to submittal of plans and details of the proposed graywater system necessary to ensure compliance with the requirements of this chapter.Identification of the groundwater level and soil absorption qualities at the site shall be included in the plans or provided to the Enforcing Agency.

  • 1605A.0 Inspection and Testing.(A) Inspection. A graywater system for which a construction permit is required shall be subject to inspection by the Enforcing Agency and such construction or work shall remain accessible and exposed for inspection purposes until approved.(B) In order to determine the absorption quantities of questionable soils other than those listed in Table 16A-2, the proposed site may be subjected to percolation tests acceptable to the Enforcing Agency. Exception: Irrigation fields in compliance with Section 1611A.2, which only utilize drip type emitters.


  • A washer machine system, without an extra pump, producing 60 gallons per day, does not need a permit.
  • Any other style of system e.g. re-using shower water, or using a pump, must have a construction permit.
  • Construction permits require a plot plan with supporting data, drawings and plans of the graywater system, and a site test by the agency after installation. If drip emitters are not used a percolation test will be required as well.

Discussion of the Implications of the California Greywater Code

Washer Machine SystemThe code does not define how the water is to get from the washer machine to the irrigation area, nor how it enters the soil (other than 2” cover must be present, and ponding / runoff must not occur).

However Laundry to Landscape (L2L) is promoted in California as a method of irrigation suitable for washer machines, and uses the pump of the washer machine to pressurize a distribution line with either holes drilled or valves connected, typically letting water out into a mulch basin.

To minimize damaging backpressure on the pump, a series of holes / valves are used, ranging from 1/4” to 1” in diameter. To avoid clogging of the holes, at least a 3/8” hole is recommended.

According to the Oasis Design calculator about 10 holes is required to avoid overloading the pump / achieving uneven distribution.

A mulch basin for a tree is typically about 4‟ in diameter, or 12.6 square feet. The total irrigated area with 10 mulch basins will be 126 square feet.

Assuming 4 people in the house, 60 gallons per day is generated. 126 square feet does exceed the soil requirements as listed in Table 16A-2 for even heavy clay soil. Table 16A-2 defines the maximum amount of water allowable for dispersal—not efficient irrigation.

However, assuming an ETo Value of 7” per month (peak summer average across the more heavily populated regions of California), the optimum irrigation area is:

Low water use plants           1,451 square feet         (c/w L2L efficiency 8%)
Medium water use plants     839 square feet            (c/w L2L efficiency 15%)

It is possible, if washing is done on a daily or every second day, that capillary irrigation effects will assist, however at best this is likely to double the efficiency of L2L up to 30% – maybe 40%.

Laundry to Landscape isn’t the only option—some graywater dripperlines (e.g. IrriGRAY) can use gravity alone to irrigate at a rate of 1 gallon per minute, per 150 feet of dripperline, covering 700 square feet of garden area with light clay soil. 300 feet of dripperline will therefore cover 1,400 square feet.

If the washing machine is run every day, or second day, the irrigation efficiency is about 90%, so much more water is saved.

This method does require the use of a surge tank (e.g. a 50 gallon barrel) which is within the Title 16A regulations.

However if you wanted to boost the speed of efficient irrigation with a pump, a permit is required.

Why did the authorities require a construction permit for a pressurized system?

We have received a number of reasons from various authorities:

  • It was considered that as soon as a pump is used, a contractor would be required, therefore a construction permit is needed.This doesn’t make sense to us, because our Australian company‟s experience is that a pump / drip system is far easier to install than the L2L method.If plumbing changes are required (e.g. to access shower graywater), the responsibility is on the licensed plumber to perform work to code.
  • For personal safety, a GFI should be installed, and as part of the inspection process, this would be checked. On this basis, any pond pump sold at  hardware / garden centers should also require a construction permit before it is installed.
  • To avoid any possibility of pressurized backflow of graywater (or contaminants) entering the potable water supply via a possible cross connection with a potable water irrigation system, a RP backflow must be installed at service entry to the property, and this needs to be checked during the inspection process. On this basis, any irrigation components available at hardware / garden centers should also require a construction permit.

Closing comments for California

We understand that changing the code in California was particularly difficult, with many stakeholders having conflicting views on the re-use of graywater.

However the code remains too difficult / expensive to achieve compliance for the water savings achieved in many counties. California needs to decide how important water conservation is, and what role it plays in enabling economic growth.