California greywater regulations live in Chapter 15 of the California Plumbing Code, and they let homeowners reuse water from laundry, showers, and bathroom sinks for landscape irrigation without treating it first. A laundry-only system needs no building permit if you follow the code’s conditions. Anything that collects from showers or bathroom sinks does need a permit, but the process stays simpler than most plumbing work. The rules are strict about how the water gets applied to the landscape, and those operational rules are where most homeowners run into trouble.
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 grease and food particles, so that water keeps flowing to the sewer or septic system.2Justia Law. California Water Code 14876
Two laundry sources also fall outside the definition in practice. Water used to wash diapers or similarly soiled garments must be diverted to the building sewer rather than the irrigation field. The same rule applies to water contaminated by hazardous chemicals from activities like cleaning car parts or washing greasy rags.3Law.Resource.Org. 2022 California Plumbing Code – Section 1503.1(F)
Three System Types and When You Need a Permit
The code sorts residential greywater systems into three tiers based on what fixtures feed them and how much water they handle each day.
- A clothes washer system collects discharge from a single washing machine only. No construction permit is required if the installation meets all code conditions. This is the laundry-to-landscape setup most homeowners install.
- A simple system collects greywater 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
- A complex system has a discharge capacity over 250 gallons per day, or serves multiple dwellings. It also requires a construction permit and typically more detailed engineering plans.4Town of Woodside. Submittal Requirements for Gray Water Systems
A family of four running a shower and bathroom sink to an irrigation field will almost always stay under 250 gallons per day. Apartment buildings and larger homes with multiple bathrooms can cross into complex territory.
Every greywater system, including the permit-exempt laundry setup, must come with an operations and maintenance manual that stays with the building for the life of the system. When ownership or tenancy changes, the new occupant must be told the property has a greywater system.5City of Pasadena. Guidelines for Permit Exempt Greywater Systems
Conditions for the Permit-Exempt Laundry System
The laundry-to-landscape exemption is conditional, not automatic. To skip the construction permit, the system must have no potable water connection and no pump external to the washing machine, and it cannot alter other building components such as structural features or electrical and mechanical systems. The washing machine’s built-in pump doesn’t count as an external pump.6East 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 the flow either to the irrigation field or back to the sewer or septic line.7Law.Resource.Org. 2022 California Plumbing Code – Section 1503.1(A) You’ll use that valve for diaper loads, heavily soiled items, and any wash with bleach or other chemicals that shouldn’t reach your soil.
Skipping the permit does not mean skipping the rest of Chapter 15. The system still has to meet every technical and operational standard, from mulch cover to setback distances. If your local building department requires notification before installation, you have to provide it. The exemption also does not override any local ordinance that applies to your property.6East Bay Municipal Utility District. California Plumbing Code – Graywater Laundry to Landscape Requirements
Design and Installation Standards
Every system has to meet technical requirements built to protect the potable water supply, prevent groundwater contamination, and keep greywater away from people.
Backflow Prevention and Pipe Identification
A greywater system cannot connect to any potable water line without a physical backflow barrier. 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 carrying non-potable water. The standard approach is purple-colored pipe or purple identification tape wrapped around existing pipe, matching California’s broader convention for recycled water lines.
Setback Distances
The code imposes minimum separations between the greywater dispersal field and various features. Seasonal high groundwater must sit at least three vertical feet below the lowest point where greywater is dispersed.4Town of Woodside. Submittal Requirements for Gray Water Systems Greywater must stay at least 100 feet from any creek, wetland, or waterway and at least 100 feet from water supply wells. The dispersal field also has to maintain at least two feet from building structures and at least one and a half feet from any property line adjoining private property.9Permit Sonoma. Setback Requirements The local enforcing agency can increase any of these distances when it identifies special hazards on or near your site.
Surge Tanks
Simple and complex systems often include a surge tank to hold greywater briefly before it flows to the irrigation field. Tanks must be solid, durable, corrosion-resistant, and watertight, with a locking gasketed access opening for inspection and cleaning. Each must be permanently labeled with its rated capacity and a warning reading “GRAYWATER IRRIGATION SYSTEM, DANGER—UNSAFE WATER.” Above-ground tanks need an overflow line connected to the sewer or septic system and protected by a backwater valve.10LADWP. California Plumbing Code – Surge Tank Requirements
Soil Testing
Before installing a dispersal field for a permitted system, you need percolation testing to confirm the soil absorbs greywater at a safe rate. The code requires a minimum of three tests spaced evenly across the proposed absorption area, with more where site conditions vary.
How You Can and Can’t Use the Water
California’s rules on applying greywater are stricter than many homeowners expect, and this is where most violations happen. The plumbing is the easy part; what you do with the water at the landscape end is where the code draws hard lines.
Containment and Cover
Greywater must stay on the property where it was generated. It cannot pond, pool, or run off the site. Any ponding or runoff is treated as a nuisance.11Law.Resource.Org. 2022 California Plumbing Code – Section 1503.1(C) Greywater also cannot be discharged into or reach any storm sewer or surface water body.
Every discharge point 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 two-inch cover is maintained.12Law.Resource.Org. 2022 California Plumbing Code – Section 1503.1(D)(E) The goal is to minimize contact between people and either the water or the irrigated soil, except for the contact needed to maintain the system itself.
No Spray Irrigation, No Root Crops
Spray irrigation with greywater is prohibited.11Law.Resource.Org. 2022 California Plumbing Code – Section 1503.1(C) No sprinklers, no misters, no overhead application of any kind. The risk of aerosolizing bacteria makes that rule non-negotiable regardless of system type.
Greywater can irrigate fruit trees, nut trees, and ornamental landscaping. You cannot use it on root crops or any edible plant where the edible part touches the soil. Potatoes, carrots, onions, lettuce, and strawberries are all off limits. Fruit trees are fine because the edible portion grows well above the irrigation point.
Storage Limits
Untreated greywater cannot be stored for more than 24 hours and has to be discharged to the irrigation field the same day it’s generated. Holding it longer lets bacteria multiply and turns a minor sanitation issue into a real one. A surge tank is sized to buffer flow across the day, 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 have to follow the daily-discharge rule.
Soap and Cleaning Product Choices
What goes into your washing machine and bathroom sinks ends up in your soil, and the wrong products can damage plants or degrade soil over time. The code addresses this only broadly, but the state’s greywater guidance flags specific ingredients to avoid.
Sodium is the biggest long-term concern. High sodium raises soil alkalinity and breaks down soil structure, slowing percolation and starving roots of air. 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 cuts sodium loading significantly.
Boron and borax deserve special attention. Plants need trace boron, but concentrations only slightly above that become toxic, which rules out borax-based cleaners. Chlorine bleach kills the beneficial soil microbes that break down organic matter and should be avoided; oxygenated bleach based on hydrogen peroxide works as a substitute. If you need to run a bleach load, divert that cycle to the sewer. Also avoid petroleum distillates, alkylbenzene, and enzymatic cleaners. Plant-based liquid soaps that are low in sodium and free of boron compounds are the safer choice.
Routine Maintenance
A greywater system is not a set-it-and-forget-it installation, but the upkeep is light. Check the diverter valve periodically to make sure it moves freely and seals in both positions. Inspect the mulch or soil cover over the discharge points at least twice a year and top it up when it drops below the two-inch minimum. If the system has a surge tank, open the access lid seasonally to check for sediment and flush the tank when needed.
Local Rules Can Be Stricter
Chapter 15 sets a statewide floor, not a ceiling. Your city or county can adopt greywater regulations more restrictive than the state code. Some jurisdictions require permits or notifications even for the clothes washer systems that state code exempts. Woodside, for example, requires a permit, drawings, specifications, and a percolation test for any greywater system, including laundry-to-landscape setups that would otherwise be permit-exempt.4Town of Woodside. Submittal Requirements for Gray Water Systems
Before buying fittings, call your local building department and ask two things: whether they require a permit or notification for a clothes washer greywater system, and whether they’ve adopted any local amendments to Chapter 15. A five-minute call can keep you from installing a system that complies with state code but violates a local ordinance.