California’s greywater regulations, set out in Chapter 15 of the California Plumbing Code, let homeowners reuse water from showers, bathroom sinks, bathtubs, and clothes washers to irrigate the landscape without treating it first. A single-washing-machine laundry-to-landscape system needs no construction permit if it meets the code’s conditions. Anything larger or drawing from more fixtures does need a permit, but the process is manageable. The rules that most often catch people out are not about the plumbing itself but about how the water can be applied once it reaches the yard.
What Counts as Greywater
Greywater is untreated wastewater that has not been contaminated by toilet discharge or by infectious or unhealthy bodily wastes. It includes water from bathtubs, showers, bathroom sinks, clothes washing machines, and laundry tubs.1California Legislative Information. California Health and Safety Code 17922.12 Water from kitchen sinks and dishwashers is excluded because of higher grease and food-particle contamination and must continue flowing to the sewer or septic system.2Justia Law. California Water Code 14876
Two exceptions catch people by surprise. Water from washing diapers or similarly soiled garments is not greywater even though it comes from the washing machine, and it must be diverted to the building sewer. The same applies to water contaminated by hazardous chemicals, such as from cleaning car parts or washing greasy rags.3Law.Resource.Org. 2022 California Plumbing Code – Section 1503.1(F) That is what the diverter valve is for.
When You Need a Permit
California sorts residential greywater systems into three tiers based on the fixtures they collect from and how much water flows through each day.
- Clothes washer system: collects discharge from a single washing machine only. No construction permit is required if the installation meets every code condition. This is the laundry-to-landscape setup most homeowners install.
- Simple system: collects from multiple fixtures such as showers, bathroom sinks, and the washing machine, with a total discharge capacity of 250 gallons per day or less. A construction permit is required.4Town of Woodside. Submittal Requirements for Gray Water Systems
- Complex system: any system with discharge capacity over 250 gallons per day, or a multi-dwelling system. A construction permit is required, and plans typically involve more detailed engineering.4Town of Woodside. Submittal Requirements for Gray Water Systems
The practical difference between simple and complex usually comes down to household size and how many fixtures feed the system. A family of four sending shower and bathroom-sink water to an irrigation field will almost always stay under 250 gallons per day. Apartment buildings and larger homes with multiple bathrooms are where the complex threshold starts to matter.
Conditions for the Permit-Exempt Laundry System
The permit exemption for a clothes washer system is conditional. To qualify, the system cannot include a potable water connection or a pump external to the washing machine, and it cannot alter other building components such as structural, electrical, or mechanical systems. The washing machine’s own built-in pump does not count as an external pump.5East Bay Municipal Utility District. California Plumbing Code – Graywater Laundry to Landscape Requirements
Every clothes washer system needs a clearly labeled, accessible diverter valve so you can send flow either to the irrigation field or to the sewer or septic line.6Law.Resource.Org. 2022 California Plumbing Code – Section 1503.1(A) You’ll use it whenever you wash diapers, heavily soiled loads, or anything with bleach.
The exemption is narrow. Your clothes washer system must still comply with every operational and technical standard in Chapter 15, from mulch cover to setback distances. If your local building department requires notification before installation, you must provide it, and any local ordinance still applies.5East Bay Municipal Utility District. California Plumbing Code – Graywater Laundry to Landscape Requirements An operations and maintenance manual is also required, and it must stay with the building for the life of the system.7City of Pasadena. Guidelines for Permit Exempt Greywater Systems
Design and Installation Standards
Every greywater system, whether permit-exempt or not, must meet the same core technical requirements.
Backflow Prevention and Pipe Identification
A greywater system cannot connect to any potable water line without a physical barrier against backflow. Acceptable devices include an air gap, a reduced-pressure principle backflow preventer, or another approved device.8Law.Resource.Org. 2022 California Plumbing Code – Section 1503.1(I) All greywater piping must be identifiable as non-potable, typically by using purple pipe or purple identification tape, consistent with California’s convention for recycled and non-potable water lines.
Setback Distances
Your dispersal field has to sit a safe distance from anything the code protects. The highest point of seasonal groundwater must be at least three vertical feet below the lowest point where greywater is dispersed.4Town of Woodside. Submittal Requirements for Gray Water Systems Greywater cannot come within 100 feet of any creek, wetland, or waterway, or within 100 feet of a water supply well. The dispersal field must sit at least two feet from building structures and at least one and a half feet from a property line adjoining private property.9Permit Sonoma. Setback Requirements Your local enforcing agency can increase any of these distances if it identifies site-specific hazards.
Surge Tanks
Simple and complex systems often include a surge tank that temporarily holds greywater before it moves to the irrigation field. Surge tanks must be watertight, built from solid, durable, corrosion-resistant materials, and fitted with a locking, gasketed access opening. Each tank must be permanently labeled with its rated capacity and the warning “GRAYWATER IRRIGATION SYSTEM, DANGER—UNSAFE WATER.” An above-ground tank needs an overflow line permanently connected to the sewer or septic system, protected by a backwater valve so sewage cannot flow back into the tank.10LADWP. California Plumbing Code – Surge Tank Requirements
Soil Testing
Permitted systems need percolation testing before the dispersal field goes in, to confirm the soil can absorb greywater at a safe rate. The code requires a minimum of three tests spaced evenly across the proposed absorption area, and more where site conditions vary.
How You Can Use Greywater
The operational rules are stricter than most homeowners expect, and this is where most violations happen.
No Ponding, No Runoff, No Storm Drains
Greywater must stay on the property where it was generated. It cannot pond, pool, or run off the site, and it cannot reach any storm sewer or surface water body. The code treats any ponding or runoff as a nuisance.11Law.Resource.Org. 2022 California Plumbing Code – Section 1503.1(C)
Two Inches of Cover at Every Discharge Point
Every point where greywater is released must be covered by at least two inches of mulch, rock, soil, or a solid shield. Greywater can be released above the ground surface as long as this cover is maintained.12Law.Resource.Org. 2022 California Plumbing Code – Section 1503.1(D)(E) The point is to minimize any human contact with the water or the irrigated soil, except for the contact needed to maintain the system.
No Spray Irrigation
Spray irrigation with greywater is flatly prohibited.11Law.Resource.Org. 2022 California Plumbing Code – Section 1503.1(C) No sprinklers, no misters, no overhead application of any kind. Aerosolizing bacteria is the health concern the code will not compromise on.
Fruit Trees Yes, Root Crops No
Greywater can irrigate fruit trees, nut trees, and ornamental landscaping. It cannot be used on root crops or on any edible plant where the part you eat touches the soil, so potatoes, carrots, onions, lettuce, and strawberries are off-limits. Fruit trees are fine because the edible portion grows well above the irrigation point.
24-Hour Storage Limit
Untreated greywater cannot be stored for more than 24 hours and must go to the irrigation field the same day it is generated. Holding it longer lets bacteria multiply, producing odors and a real sanitation problem. A surge tank is sized to buffer daily flow, not to stockpile water. Treated greywater from a complex system with filtration and disinfection can be stored, but most residential systems use untreated water and follow the daily-discharge rule.
Products That Are Safe to Send Through the System
What goes into your washing machine and bathroom sinks ends up in your soil. The California Department of Water Resources’ greywater guidance flags specific ingredients to avoid.
Sodium is the biggest long-term concern. High sodium raises soil alkalinity and breaks down soil structure, making it harder for water to percolate and roots to breathe. Powdered detergents are worse than liquid ones because they contain sodium-based fillers on top of the sodium already in the cleaning agents. Switching to liquid soaps and detergents reduces sodium loading significantly.
Boron and borax deserve special caution. Plants need trace amounts of boron, but concentrations above that quickly become toxic. Chlorine bleach should be avoided because it kills the soil microbes that break down organic matter; oxygenated (hydrogen peroxide-based) bleach is a workable substitute. If you have to run a bleach load, use the diverter valve and send that cycle to the sewer. Petroleum distillates, alkylbenzene, and enzymatic cleaners are also worth avoiding. Plant-based liquid soaps low in sodium and free of boron compounds are the safest choice.
Maintenance and Freeze Protection
A greywater system is not set-it-and-forget-it, but the upkeep is light. Check the diverter valve periodically so it moves freely and seals in both positions. Inspect the mulch or soil cover over your discharge points at least twice a year and top it up when it thins below two inches. If your system has a surge tank, open the access lid seasonally, check for sediment, and flush the tank if needed.
In colder parts of California, including mountain and high-desert communities, freezing temperatures can damage exposed pipes, valves, and tanks. Bury irrigation lines below the frost line, insulate tanks and exposed valves, and slope pipes so water drains after each use rather than sitting stagnant. In areas with sustained hard freezes, the simplest approach is to divert to the sewer during peak winter and switch back in spring.
Check Your Local Rules Before You Build
The California Plumbing Code sets a statewide floor, not a ceiling. Cities and counties can adopt greywater rules that are more restrictive than Chapter 15. Some jurisdictions require permits or notifications even for clothes washer systems that the state code exempts. The Town of Woodside, for example, requires a permit, drawings, specifications, and a percolation test for any greywater system, including laundry-to-landscape setups that state code would otherwise exempt.4Town of Woodside. Submittal Requirements for Gray Water Systems
Before you buy fittings, call your local building department and ask two questions: whether they require a permit or notification for a clothes washer greywater system, and whether they have adopted any local amendments to CPC Chapter 15. A short phone call now can prevent an installation that meets state code but breaks a local rule.