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Graywater information

• Common mistakes & preferred practices
• Graywater Q&A
• Graywater links
• Consulting
• Wild Water Wisdom (article)
• Indoor grey water reuse
• Builder's action summary
• Gray water workshop
• sistemas para aguas grises (en Español)
• Greywater in cold climates

Graywater books

• The New Create an Oasis with Graywater (book)
• Builder's Graywater Guide (book)

System examples

• Laundry to Mulch Basins
• System selection chart (PDF)
• Branched drain system explanation
• Branched drain system example (PDF)
• Branched drain in indigenous community
• Manual graywater systems of Huehuetortuga
• Gravity drum

Graywater regulation

• Grey water policy center
• California greywater policy center
• How to improve California and Uniform Plumbing Code (UPC) graywater laws
• How to improve International plumbing code (IPC) graywater law
• Reward for permitted system plans
• How to inspect or construct legal stub outs for a future graywater system
• Fecal coliform measurements
• Monitoring Graywater Use: Three Case Studies in California (pdf)
• Reward for permitted systems

What is graywater ?

Any washwater that has been used in the home, except water from toilets, is called graywater . Dish, shower, sink, and laundry water comprise 50-80% of residential "waste" water. This may be reused for other purposes, especially landscape irrigation.

(This is the definition common in Europe and Australia. Some jurisdictions in the US exclude kitchen sink water and diaper wash water from their definition of greywater. These are most accurately defined as "dark graywater ")

Why use graywater ?

It's a waste to irrigate with great quantities of drinking water when plants thrive on used water containing small bits of compost. Unlike a lot of ecological stopgap measures, graywater reuse is a part of the fundamental solution to many ecological problems and will probably remain essentially unchanged in the distant future. The benefits of graywater recycling include:

• Lower fresh water use
• Less strain on failing septic tank or treatment plant
• Better treatment (topsoil is many times more effective than subsoil or treatment plant)
• Less energy and chemical use
• Groundwater recharge
• Plant growth
• Reclamation of otherwise wasted nutrients
• Increased awareness of and sensitivity to natural cycles

Why Does Greywater Matter?

Viewed narrowly, greywater systems don’t look that important. A low flow showerhead can save water with less effort. A septic system can treat greywater almost as well.
But when you look at the whole picture—how everything connects—the keystone importance of greywater is revealed.

• Ecological systems design is about context, and integration between systems. The entirity of integrated, ecological design can be reduced to one sentence: do what's appropriate for the context.
  
• Ecological systems—rainwater harvesting, runoff management, passive solar, composting toilets, edible landscaping—all of these are more context sensitive than their counterparts in conventional practice; that's most of what makes them more ecological.
  
• Greywater systems are more context sensitive than any other manmade ecological system, and more connected to more other systems.
  
• Get the greywater just right, and you’ve got the whole package right—and that matters.

Many people and organizations instinctively recognize that greywater is the ideal test case for the transition to a new way of regulating and building that is appropriate to a post-peak resource, mature civilization.

The US Green Building Council, the City of Santa Barbara, CA, Oregon ReCode, and SLO Green Build are among those organizations which independently chose greywater standards as the technolgogy with which to launch thier programs of regulatory reform.

Is graywater reuse safe?

Yes. There are eight million greywater systems in the US with 22 million users. In 60 years, there has been one billion system user-years of exposure, yet there has not been one documented case of greywater transmitted illness.

(In contrast, 400 Americans get hit by lightning each year. More details, calculations and references).

Is graywater legal?

In practice, greywater legality is virtually never an issue for residential retrofit systems—everyone just bootlegs them. However, graywater legality is almost always an issue for permitted new construction and remodeling, unless you're in a visionary state such as Arizona, New Mexico, Texas (and soon, NV, MT, OR, and CA). For details see our Grey water policy center and Builder's Graywater Guide (book).