Graywater is lightly used water from clothes washers, showers, bathtubs, and bathroom sinks. It contains some soap and detergents but it’s a safe and effective water supply for most landscapes. Water from toilets or wash water from diapers is never considered graywater. Kitchen sink water is not considered graywater in California. Graywater is not the same as recycled water. Graywater should never be stored longer than 24 hours, unlike rainwater.
You can attend our four-part virtual graywater workshop to learn about graywater at your convenience.
Why Use Graywater?
With a graywater system, you can save water, time and money every time you wash a load of laundry or take a shower. It’s a reliable, local and drought-resilient water source to protect your landscape of hotter summers and dryer winters. Graywater can also decrease water and wastewater utility bills and extend the life of the septic system leach fields.
Another benefit of using graywater is that it connects us to our water supply, helping us understand where our water comes from and where it goes. Becoming conscious of our water supply encourages healthier product choices and engagement with our landscapes. In concert with water conservation, climate-appropriate landscaping, and rainwater harvesting, using graywater helps reduce dependency on imported water and protects the urban watershed.
How much water does graywater save?
On average, Laundry-to-Landscape systems can save approximately 17 gallons per person per day or 14,565 gallons per household a year! (2012 report by Greywater Action in collaboration with the City of Santa Rosa and Ecology Action of Santa Cruz) This is enough water to irrigate 800 square feet of trees, shrubs, and vines in most climates. The actual amount of water you may end up saving from using graywater depends on:
- How much graywater you actually produce, and
- How much water you use in your landscape that can be replaced with graywater.
Up to 60% of a home’s indoor water use may become graywater and about 50% of all water is used in the landscape--that is a lot of potential savings by sending graywater into your yard!
How much water does a graywater system cost?
The amount really depends on site-specific conditions, but in general, a laundry-to-landscape system installed by a contractor will cost between $1,500-$2,500 (the material cost is typically covered by the rebate amount). All other graywater systems increase in complexity, cost, and regulatory hurdles: a whole-house graywater system may cost upwards of $15,000 excluding permitting costs and backflow-protection requirements.
Types of Graywater Systems
A graywater system can be as simple as a bucket collecting shower water or as complicated as a whole-house system with pumps, filters, and treatment. The simpler the system, the lower the cost and easier the maintenance. All graywater must be applied subsurface and stay within your property boundaries (no runoff).
As you begin learning about graywater, some resources may be found with alternate spellings like “greywater”, “grey water” and “gray water”. Government agencies tend to spell graywater with an “a” while nonprofit organizations tend to spell greywater with an “e”.
A simpler type of graywater system that qualifies for a Valley Water rebate or direct installation assistance. They are sustainable, cost-effective and drought-resilient graywater systems that redirect water from your clothes washer to your landscape without additional pumps or filters or permits in most situations. Graywater Laundry-to-Landscape systems are sometimes abbreviated as just “graywater L2L systems”, “Laundry-to-Landscape systems”, “laundry graywater systems” or “clothes washer graywater systems”.
Due to its relative simplicity and the assistance Valley Water provides to install them, this is the best system to start considering.
To learn more about how to start using a laundry-to-landscape system, click here.
Graywater from Showers, Baths, or Bathroom Sinks
A bucket to collect shower warm-up water is the most cost-effective option unless you’re building a new home or remodeling your bathroom. Branched Drain systems are similar to Laundry-to-Landscape systems, but they’re effectively gravity-powered graywater systems. More complicated systems are available with pumps and filters, yet those add additional costs, rules, permit requirements and maintenance considerations.
Whole-House Graywater Systems
The Alliance for Water Efficiency offers an overview of whole-house graywater systems, general information on codes and costs, system maintenance considerations, and more. For information on equipment for these non-rebate graywater systems that will require a permit, visit the following Greywater Action links:
Toilet-flushing Graywater Systems
In general, it’s more cost-effective and sustainable to replace your toilets with the most-efficient toilets on the market. Toilets that reuse graywater from a sink directly above it are on the market as well. Rainwater to flush toilets [PDF] is a more cost-effective and long-term option to consider.
The California Plumbing Code allows graywater to be used for flushing toilets but the graywater must be treated to meet certain water quality requirements. These systems require a permit, inspection and cross-connection control so please check with your local city planning or building department for more information.
Since even relatively clean graywater (like from your clothes washer) has particles, lint, hair, etc. it’s essential to not only filter but regularly maintain them. Graywater for toilet flushing is more appropriate in commercial or other high-density properties where dedicated staff can maintain it over time.
In general, toilet-flushing greywater systems usually require frequent maintenance, manual cleaning of filters, and chemical disinfectant to prevent odors in the bathroom. They also tend to be relatively complicated, and it’s critical that they be designed and installed properly. If you are considering such a system try to find people to talk to who’ve had the systems installed in their homes for at least a year, and be sure to find out the maintenance requirements of the system. Consider maintenance contact with the installer (if you can afford it) for any system that requires more than annual maintenance. - greywateraction.org
Read more about Manufactured Graywater Systems (whole-house and toilet-flushing graywater systems) and specifications visit at greywateraction.org.
Is a graywater system right for you?
Maintaining a healthy soil, choosing the correct detergents, and using best practices for designing, installing, and maintaining your system is key to keeping your landscape healthy.
Knowing the signs of stress from sodium- and boron-accumulation can help resolve symptoms before a problem becomes pervasive. The following questions can help you understand whether or not you should invest in a graywater system.
Do you have a reverse-osmosis (RO) system or use water softener?
Reverse Osmosis Systems
Free of minerals and salts, an RO system's water is graywater-friendly (just send the RO concentrate to the sewer).
If you have a water softener, consider using a potassium-based water softener instead of sodium-based, bypassing the clothes washer from the softened water, adding a reverse-osmosis system, or trying alternatives to conventional ion-exchange water softeners [PDF and study evaluating water-softener alternatives].
What’s the difference between sodium chloride and potassium chloride water softeners?
- Salt, or sodium chloride, is commonly used in water softeners to remove the hardness from water in homes and businesses. Potassium chloride works exactly the same way that sodium does in the water-softening process. However, there has been a slow but steady growth in the use of potassium chloride (KCl), which is chemically related to salt and has the same water-softening characteristics. Most water softeners remove hardness (calcium and magnesium) and iron from water through an ion-exchange process. The harder the water, the more sodium or potassium respectively is added to effect softening.
How does potassium chloride benefit the environment?
- Potassium chloride is a naturally occurring mineral, and it is often marketed as agricultural plant food. Sodium can be harmful to plants, whereas potassium is an essential mineral for plant growth. By switching from sodium chloride to potassium chloride, it will reduce sodium and chloride being discharged into municipal wastewater treatment facilities, thus enhancing the quality of recycled water and soil conditions.
How do you change regenerants?
- If you switch from using salt to potassium chloride, you may just add the potassium chloride pellets into the tank where salts are added. No equipment changes or adjustments are required for most household water softeners; however, please refer to your owner’s manual or contact manufacturers for compatibility. Also, please consult your physician if you have any health-related questions about consuming potassium chloride-treated soft water.
Do you have a septic system?
Every septic system is different, but you may need less frequent leach field replacement [PDF] by sending more of your laundry rinse water to the landscape with a graywater system. Graywater systems should be at least 5-feet away from a septic system’s leach field.
What kind of soaps and detergents are graywater-safe?
In General, detergents containing Boron, bleach, antibacterial compounds, and fabric softeners can degrade the health of your landscape's soil over time.
A graywater-safe soap and detergent list from Greywater Action. This list is based on their experience and expertise working with graywater-irrigated landscapes and not a specific recommendation. When product labels aren't sufficient, these general tips and these additional graywater resources can help find graywater-compatible or garden-friendly detergents.
Since soaps and detergents contain a variety of chemicals to aid in cleaning, inquire with the County’s Department of Environmental Health, the California Department of Food and Agriculture, and University of California Division of Agriculture and Natural Resources for additional information if you choose to use graywater on food you may eat and you are unsure of the soaps or detergents in your graywater. To minimize potential health and safety concerns, look for “graywater-compatible”, “garden-friendly”, and “dioxane-free” detergent labels.
What kind of plants can I irrigate with graywater?
Graywater is better for certain plants compared to others: Decorative trees, fruit trees, shrubs, vines, California-native riparian plants and hardier native plants perform well. Very advanced and expensive subsurface drip systems can irrigate lawns with graywater when properly permitted and designed. Keep it simple before considering more advanced options.
Never use graywater to irrigate fruits or vegetables that come in direct contact with graywater or the soil surface, such as root vegetables like potatoes or carrots.
Laundry-to-Landscape System Rebate
Follow our rebate guide to plan and start using your graywater from your laundry to water your landscape. Click Here
These listed videos provide tips on how to safely use graywater and overviews of different types of graywater systems:
Sustainable Gardening with Graywater (California Water Efficiency Partnership). Not a local resource, use this for general information only.
Graywater Laundry to Landscape Systems Overview (California Water Efficiency Partnership; San Diego County Water Authority)
Overview of Graywater System Options for Residential Use (City of Tucson). Not a local resource, use this for general information only.