By Kat Sawyer
As Californians, we are painfully aware of persistent drought concerns. But did you know that even though the earth’s surface is 70% water, 97% is ocean and most of the 3% remaining fresh water is inaccessible in ice or groundwater? Only 1% of water on earth is available for human use! All the more reason to conserve and reuse water wherever we can. In our homes, 2 of the 3 most water intensive activities are laundry and landscaping, so when we connect them we are conserving and reusing at the same time.
Laundry-to-Landscape graywater systems are low tech and LEGAL, and they can be installed without a permit because no plumbing is altered. Exhaust water from your washing machine is simply redirected to your backyard into mulch basins dug around the drip line of plants. The East Bay Municipal Utility District and San Francisco Public Utilities Commission have programs that subsidize the parts required for installation.
Indoors above your washing machine, a brass 3-way diverter valve is installed with the laundry hose connected to the middle port. 1” PVC pipe is attached to either side of the valve, sending one side to your landscape. The other side recreates the existing condition of your laundry setup, sending water from the washing machine into the sewer standpipe or utility sink.
The pump inside your washing machine propels the water in whichever direction you choose as it spins to empty, allowing you to irrigate fruit trees and hearty plants in your backyard or send it to the sewer if you’re using bleach in your wash. This gravity-fed system can pipe graywater 50 feet on a flat surface but should not be used on uphill inclines.
When planning a graywater system, it is important to analyze your soil type so that you know how quickly water will infiltrate into the ground. This determines how many mulch basins you will need, along with factors such as loads of laundry per week and whether you have a front loading or top loading washer. A percolation test is a quick way to learn about your soil. Dig a 1-foot hole, fill it up with water and measure how much drains per hour. The hole must drain at least 1” per hour. Graywater should not pond or be stored longer than 24 hours, so soils with high clay content require bigger mulch basins than sandy soils where water drains quickly.
If you want to dig deeper into your soil content, you can do a Jar Test. This can be a fun scientific activity for children. Collect a sample of dirt in a jar with a lid, add water and shake it up. Rocks and sand will settle to the bottom immediately. The silt layer will settle in a couple of hours, but the clay layer will take days, only revealing itself when the water clears.
Important things to consider when designing your L2L system:
- L2L systems require plant-friendly detergents with no sodium or borate.
- The 3-way valve should be labeled with an on/off photo or diagram showing which way the water goes.
- Graywater is best for fruit trees and plants with large root zones, but cannot be used on root crops like potatoes or carrots.
- Graywater is not recommended for native plants (drought tolerant) or well-established trees that have found their own groundwater source.
- Discharge graywater 2” below the surface so that it doesn’t come into contact with people or animals.
- Prevent roots from clogging the outlet pipe by using a special mulch shield box that provides a 4” gap from the pipe to the mulch.
- Keep mulch basins set back 2 feet from buildings and 18” from property lines.
- For backyards with existing irrigation systems, find a zone that you can shut off and replace with graywater.
To learn more about Laundry-to-Landscape systems, check out the book “The Water-Wise Home” by Laura Allen.