General Greywater FAQ

Greywater is water that drains from your bathroom sinks, showers, tubs and laundry. Water from toilets, kitchen sinks and dishwashers is considered blackwater and cannot be re-used.

Greywater can be used primarily to irrigate plants in the landscape. On larger projects (multi-family/ commercial/institutional) greywater can be used for toilets flushing, if treated with advanced filtration and disinfection.

Greywater is safe! Greywater contains water, dirt and a multitude of biological inhabitants (bacteria, viruses, etc.) that live on our bodies and clothes. The majority of these biological inhabitants are beneficial, but pre-cautions should be taken to ensure that humans and animals do not come into direct contact with greywater, so as to avoid any potential health concerns. Greywater should always be applied to the landscape at least 2” below the soil surface, and should not be allowed to pool on the soil surface.

Yes! Prior to 2009 greywater systems were illegal in most states. This is changing rapidly and many states have adopted building code regulations which legalize greywater systems. States which currently allow greywater systems are California, Arizona, Nevada, Washington, Oregon, New Mexico, Utah, Texas, Colorado and more.

Bio-degradable and non-toxic cleaning products should be used with greywater systems for irrigation use. Avoid products with a high salt (sodium) content and boron (borax), two common ingredients that are non-toxic to people but harmful to plants. Bar soaps can make greywater Alkaline, so use liquid soaps to maintain a neutral water pH. Anti-bacterial soaps should be avoided as they may kill beneficial soil bacteria. Liquid laundry detergents have less salt than powdered detergents.

Most plants thrive in greywater, including most drought tolerant plants which like alkaline soils. Greywater tends to be alkaline (pH 7.5-9) so acid loving plants (rhododendrons, azaleas, etc.) may need additional supplements to maintain more acidic soil after many years of greywater irrigation.