Our Zone 7 team answers frequently asked questions on greywater systems.
What is greywater (or graywater)?
Greywater is lightly used water from indoor sources that can be collected and reused for irrigation or other non-potable uses. Household sources include clothes washers, bathroom faucets, showers, and bathtubs. Water from toilets or wash water from diapers is never considered greywater because it may contain pathogens.
What are greywater systems?
Greywater systems are used to collect greywater for reuse. They generally cannot include any water from toilets, kitchen sinks, or dishwashers. At its simplest level, a household can collect laundry water or other greywater manually using buckets, and use the water for irrigation.
More formal Laundry-to-landscape (L2L) systems reuse water from laundry machines. Compared to other types of greywater systems, L2L systems have the simplest and most affordable installation. Generally, permits are not required to install a L2L system if the system does not alter the household plumbing and is installed on a one or two- unit residential building.
Simple and complex systems differ from L2L systems because they reuse water from a bathroom sink, shower, and/or bathtub and alter the building’s plumbing and can include surge tanks, filtration systems, and pumps. Simple greywater systems generate less than 250 gallons of irrigation water per day, while complex systems generate over 250 gallons.
Are there regulatory requirements for greywater reuse?
Greywater systems are regulated under Chapter 15 of the California Plumbing Code.
Why reuse greywater?
- Landscaping irrigation is often the single biggest category of urban water use, accounting for up to 70% of total water urban use, particularly in warmer inland areas like the Tri-Valley. Ideal for irrigating landscaping, greywater can make good use of about 60% of indoor water that is appropriate for reuse.
- Greywater reuse helps preserve drinking water supplies by limiting the amount needed for landscape irrigation. Reusing this local water source reduces dependency on imported water.
- Greywater can be a reliable supply of water for your plants, especially during water shortages or droughts.
- Outdoor greywater use requires no treatment. Simple L2L systems are inexpensive to install and do not require a permit.
- Greywater contains nutrients that can be good for your plants so it’s a nice way to recover this resource.
- Greywater systems can reduce overall water consumption and potentially your water bill.
- Reusing greywater reduces the amount of wastewater entering sewers or treatment systems.
- Greywater reuse connects us to our water supply, helping us understand where our water comes from and where it goes and helping us become better stewards of our watershed.
What can you do to ensure safe and environmentally responsible greywater reuse?
- Choose appropriate plants that can handle the volume of water for irrigation.
- Ensure your irrigated area is sited properly—greywater systems can send water about 50 ft across a flat landscape and even further downhill. Not recommended if your property is within 100 ft uphill of a creek.
- Use a “plant-friendly liquid laundry detergent” that is low in salts, biodegradable, and cannot contain boron or chlorine bleach.
- Manage your greywater system to prevent over-watering, for instance during the rainy season, or when washing laundry loads containing cloth diapers or similarly soiled/infectious garments.
- Don’t reuse greywater if you have a water softener. Most water softeners will produce water with high salt levels that will harm plants.
How can I start reusing greywater?
An easy way to start is by using a shower bucket to collect the cold water from your shower as it warms up, and then use it to flush your toilet or water your garden!
For specific information on greywater systems where you live, or potential rebate opportunities, visit your City’s or water retailer’s website:
Are there rebates available for greywater systems?
Livermore Municipal Water is now offering rebates up to $50 for their customers to install laundry-to-landscape greywater systems.
Zone 7 Water Agency, a wholesale water agency in the Tri-Valley, currently does not offer rebates for greywater systems but will consider developing one as part of our conservation rebate programs. Visit Zone 7’s website for information about rebates.
San Francisco Public Utilities Commission Graywater Program
East Bay Municipal Utility District Graywater Resources
City of Livermore Laundry-to-Landscape Greywater System Rebate