What is Graywater?

Graywater Gardening
From Buckets to Irrigation Systems

What is Graywater?

(back to Why Graywater?)

The average person uses over 25 gallons per day for simple tasks such as bathing or showering, and using the clothes washer machine.

This doesn't sound much, but over one month this amounts to over 750 gallons per person.

Graywater is household waste water that includes the following:

Shower Water
Bath Water
Lavatory (basin) Water
Laundry Water
Untreated Spa Water

Typically, two thirds of the water used in a house results in graywater (excluding water used for the garden and lawns).

Blackwater is household waste water that includes:

Toilet Water
Laundry Water, if the waste water is from washing diapers, or other materials containing feces

Darkwater is household waste water from the kitchen. It may contain food contaminants, oils and powerful detergents (especially dishwashers).

Although many jurisdictions ban the re-use of kitchen water (Darkwater), in some situations this water may be used for garden irrigation IF a grease trap is installed between the kitchen waste outlet and a graywater pumping system.

The above definitions apply generally throughout the world, although exact definitions vary from country to country, and in the US from state to state.

Practical Graywater Re-use

In an urban situation, with a utility provided sewage system, we recommend only re-using shower, bath, spa bath and laundry water. Kitchen and lavatory water is best left for the blackwater waste pipe network. Lavatory water is in most cases does not provide enough water to justify the connection cost, and in any case provides additional water flow to help flush the blackwater pipe system.

In a rural situation (i.e. a septic system is used), kitchen water can be used (subject to local regulations), IF the following occurs:

A grease trap is installed between the kitchen sink and the graywater system. This ensures food scraps, fats and oils are irrigated in the garden. In addition to containing high bacteria levels, the significant quantity of fats can create an impervious barrier within the top soil.

The dishwasher does not empty into the kitchen sink waste, because the detergent is too caustic.

Graywater Names

Graywater is called Graywater, Gray Water, Greywater & Greywater. Although debate is still underway (and will probably never cease), the likely outcome is Graywater in the US, and Greywater in other countries. Fortunately most search engines now search for all of the above terms if only one is searched.

Further Information about graywater:

How can graywater be re-used?

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