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Reusing Your Gray Water: State Laws Vary for Homeowners

Tuesday, July 26, 2011

By Alex Keller, EWG Summer Water Analyst

Recently, we took a look at the water-saving potential of residential "gray" water, which, naturally, leads people to wonder: Can I use this technology in my home, too?

The answer? It depends.

Some states stricter than others Nearly all states have long required that households dispose of used water through the sewer system, no matter its quality and purpose. Georgia exemplifies the antiquated status quo in gray water law: all used water must be filtered and treated like sewage. Homeowners who want to use gray water -- water from baths, showers and laundry -- would have to install a full-fledged treatment system. This makes no financial sense, so they don't. But recently, the U.S. Environmental Protection Agency endorsed gray water use in order to conserve fresh water, and some states have been moving to relax their laws to permit gray water to be channeled to landscaping and toilets. Several states -- California, New Mexico and Texas -- are encouraging responsible gray water use in order to alleviate water shortages in drought-prone regions. The added benefit: they reduce the amounts of chemicals being used in wastewater treatment.

But individual state laws vary widely. For instance:


  • California and New Mexico permit do-it-yourself projects that meet basic health standards. California, New Mexico and Texas allow surface drip irrigation of plants if it minimizes contact with humans and domestic animals and doesn't lead to ponding or runoff.
  • Other states, among them Arizona and Utah, have intricate regulations that make the installation of home gray water systems prohibitively difficult, specifically:
Arizona has separate laws for surface and subsurface gray water use - with "surface" defined to mean soil to a depth of two feet. The state requires a filtration device and a settling tank to separate solids from gray water. Fecal coliform levels in gray water released within two feet of the ground's surface must be monitored daily. This task is not feasible for most homeowners.


Utah allows only subsurface drip irrigation. A local health department must clear the design before its installation.


When considering a gray water system, research your local wastewater laws carefully. Every state has its own set of regulations and guidelines, and municipalities often add more restrictions.

Where your gray water comes from and where it goes matter Gray water includes untreated water from bathtubs, showers, bathroom sinks and washing machines, although specific definitions vary from state to state. Most gray water definitions don't include:


  • Kitchen sinks and dishwashers, because the water contains food waste;
  • Garage drains and other drainages likely to be contaminated with toxics or hazardous chemicals.


In some communities, gray water may be used for drip irrigation and toilet flushing. Building systems for these purposes is relatively simple.

In other places, you can use gray water only for underground irrigation. That means you must construct trenches and subterranean drainage fields that meet restrictions to protect the water table, flood plains, nearby water bodies and land uses. A gray water system usually has a holding tank to regulate flow and maintain releases within legal limits. Most states that permit gray water use require that these tanks be covered or enclosed to prevent them from becoming breeding places for mosquitoes and from creating other water-related health problems.

Gray water pipes and tanks generally must be labeled as such and frequently must read "non-potable" to prevent accidental consumption.

Increasingly, gray water laws focus on results, not design. By establishing clear, simple safety expectations for residential gray water systems, states and municipalities can minimize paperwork, technical details and headaches for everyone involved.

How to install a gray water system Guides for DIY-gray water systems are plentiful. Many are free and accessible online through states and municipalities or from manufacturers of gray water recycling equipment.

Here are a useful few sites:



Prefabricated gray water systems can cost a few thousand dollars, so they may not be for everyone. Some locations like Arizona offer government rebates to offset installation costs.

Even if a gray water system is not for you, you can save water around the home by using classic strategies such as running your washer when it's full and aiming outdoor sprinklers judiciously.

Have you installed a residential gray water system? If so, please share your experiences! Here's one personal account to learn from.

[A big thanks to Flickr CC and krikit for the hose water pic.]

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