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Graywater or Greywater, Reusing Waste Water is a Good Thing


One type of graywater system recycles water from your washer for landscape use.  Credit: Pasadena Water and Power
One type of graywater system recycles water from your washer for landscape use. Credit: Pasadena Water and Power

Graywater is untreated wastewater from bathroom tubs, sinks, showers, and washing machines. Untreated water from sources such as kitchen sinks and dishwashers, which may have properties that encourage pathogens, is called dark graywater. Water from toilets and washing machines used to launder diapers or chemically contaminated clothing is called blackwater. Simple graywater systems include the “laundry to landscape” type which does not require notification or permits by Marin County Environmental Health Services (EHS) or Marin County Building and Safety (B&S).

What are the advantages?

Save on irrigation. Recycling graywater to irrigate the garden can reduce the community’s water and energy costs. 
Save potable water. It also reduces the amount of precious drinking water from disappearing into the landscape. 
Reuse as much as 50% of residential water consumption. An estimated 30% to 50% of residential water usage produces graywater. That’s 90 gallons a day for a typical household of 2.6 persons.

Read up more on graywater!


How to use graywater

Water ornamentals with gray water which is often rich in nutrients.
Check your plants first -  Acid-loving plants won’t tolerate salts found in high pH graywater. Evergreen trees are often more salt-sensitive than deciduous trees.
Alternate graywater irrigation with fresh water to minimize salt build up.
Watch what you put in the wash. Use biodegradable pH balanced, sodium-free, boron-free, chlorine-free products in the washing machine and for bathing. 
Apply graywater directly to the ground – don’t allow it to be sprayed on plant surfaces.
Use graywater within 24 hours after collecting to minimize bacterial growth.


No contact - Avoid graywater contact with skin.
Don't use on edible plants. Avoid using graywater in the vegetable garden, particularly on root vegetables like carrots and onions. 
Don't use on lawns - Don’t use graywater on your lawn.

For detailed information
regarding graywater and its use in Marin County:
Graywater, Laundry to Landscape
Graywater Systems, County of Marin