Graywater Systems

One of the best things about living in San Diego is growing your own oranges, lemons, limes and avocadoes. One of the best ways to irrigate trees is to use graywater — the water used in your home that is safe to reuse.


Graywater is the water that drains from your clothes washer, shower, bath and bathroom faucet. It’s reusable because it only contains detergent and personal cleaning products.


Water That’s Not Reuseable

Water from a toilet, or the washing of diapers is not reusable. Water from the kitchen sink and dishwasher is unusable, as well, because of the grease and bacteria it can contain.


What You Can Irrigate With It

Use graywater to irrigate any of your plants and trees except vegetables that grow in the soil, like carrots, or on the soil, like cucumbers. Help your plants by switching to biodegradable and non-toxic laundry detergent and shampoo that is free of salt and boron. And, when you use chlorine bleach, send the water to the sewer, not your landscape.


Legal Requirements

To avoid potential contact with people and pets, don’t spray graywater from a hose or sprinkler, or allow it to pool or run off your property, and cover discharge points with at least two inches of mulch, gravel or soil. Modifying your home’s plumbing or using a pump will require a building permit and the installation of a backflow prevention device.


People have been using graywater for years and it’s time for the rest of us to start.

There Are Two Types of Systems

Laundry to Landscape System

A laundry to landscape system reuses the water from each load of laundry. Installing a 3-way valve on the wall behind the clothes washer allows you to send the draining water to the sewer or to your landscape (see diagram below). The advantage of a laundry to landscape system is how easy it is to install and use.

Whole House System

A whole house, or branched drain system, allows you to irrigate with water from your shower, tub and bathroom faucet, as well as laundry.  You will need a professional plumber to modify your sewer line. The advantage of a whole house system is that it provides much more graywater for your landscape.

There Are Two Approaches

The Traditional Approach

Traditionalists recommend not using pumps, filters, holding tanks or drip irrigation fixtures because what is in graywater — hair, thread, kleenex — can clog the system.

Pros of This Approach
A traditional system costs from $500 to $1,500 to install.

Because you rely on the pump in your clothes washer and gravity to distribute the graywater, you can only irrigate downhill from your home. A downhill grade of 2 percent is sufficient.

Using New Technology

Increased demand for graywater systems has brought new products to the market. These new, whole house systems employ pumps, filters and holding tanks (see diagram below).

Pros of This Approach
You have graywater to use every day, you can irrigate uphill from your home, and irrigate with it when you want to.

These systems can cost up to $15,000, and use of a pump requires a building permit and a backflow prevention device.

Key Questions

Is a Permit Required?

City of La Mesa

Laundry to Landscape System
A permit from the city is not required

Whole House System
A plumbing permit is required

Who to Call
Jessie Wu, Building Official

City of Lemon Grove
  1. Laundry to Landscape System
    A plumbing permit is required

Whole House System
A plumbing permit is required

Who to Call
Building Department

City of El Cajon

Laundry to Landscape System
The city does not require a permit but would like homeowners to contact them prior to discharging graywater into the landscape.  The discharge, or potential discharge of graywater into the storm drain system on the street is illegal.

Whole House System
A plumbing permit is required

Who to Call
The Building and Fire Safety Group

County of San Diego

Laundry to Landscape System
A permit is not required

Whole House System
A construction permit is required

Who to Call
Department of Environmental Health, Land and Water Quality Division

Is a Backflow Prevention Device Required?

Pumping of non-potable water sources on a property served by a public water system presents a cross-connection contamination risk, according to California’s Health and Safety Code. If you install a pump, Helix requires the installation of a backflow prevention device on the potable water service to your property. Call 619-667-6224 or email

How Much Graywater Do You Produce?

Estimate the amount of graywater you will produce based on the number of people living in your home, your graywater collection points (clothes washer, shower/bath, faucets), and the amount of graywater produced daily and weekly by each person.

How Much Graywater Do You Need?

Count the number of trees and plants you want to irrigate with graywater, and only include plants downhill from your home if your system will not include a pump. Also count the number of graywater outlets you will need within each tree’s and each plant’s root zone.

Do Supply and Demand Match Up?

You don’t want to produce more graywater than you can use because, per the California Plumbing Code, graywater must be contained on the site where it is generated and runoff on to the sidewalk or into the street is illegal. These codes are designed to minimize the opportunity for children and pets to interact with graywater.

Learn More

We recommend reading the Graywater Design Manual developed by the San Francisco Public Utilities Commission. The manual discusses each type of graywater system a homeowner can install and diagrams simplify the information.

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