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Project Grey Water

From taking a bath to watering your lawn

What do you do with the water that remains after a long, hot bath? Send it down the drain, most likely. Before you pull the plug in your bathtub, consider reclaiming the sudsy but still valuable H2O to water your lawn. Sound strange? It’s not. Millions of Americans are reusing their “grey water” everyday to water their landscape, saving gallons of H20 and pocketfuls of money.

Amidst severe drought, California recently made some changes to its grey water laws so that more citizens can partake in this eco-friendly practice. Californians can now install simple greywater reuse systems without buying a construction permit or paying installation fees which should dramatically increase the number of of grey water recyclers. In California alone, an estimated 1.7 million water-reuse systems are installed, most of which were technically illegal because homeowners avoided paying permit fees. With the passage of California Assembly Bill 313 these consumers most likely would now be legal.

What exactly is graywater?

Grey water is untreated H20 from your house that has not been in contact with toilet waste, like used water from baths, showers, bathroom sinks, and washing machines. Grey water does not include that from kitchen sinks, toilets, and dishwashers. This is called blackwater, which needs to have a separate plumbing system due to high bacterial content which is unsuitable for irrigation.

Why is it so important for you and water conservation?

According to California state officials, an average home produces 160 gallons of grey water per day, or 60,000 gallons per year, most of which is not reused; however, if a family of four reused graywater from washing machines, they could save 22,000 gallons of water a year. By reusing greywater to irrigate landscaping and to fill toilets, you can conserve water, and reduce your water and sewer bills. About 60% of your home’s water outflow is graywater which you can reuse, even during droughts when outdoor water may be limited. Graywater is used for landscape irrigation which can keep your lawn looking pristine, adding value to your home.

How to get started

To reuse grey water, your home first needs a special system that separates grey water from blackwater. Before California’s graywater laws were revised, a construction permit was required to install even a simple system, however, the urgency of California’s water situation eliminated this requirement and, along with it, permit fees. Simple graywater-reuse systems are used to collect water from a single drain attached to a washing machine, showers, or other acceptable sources. Homemade systems can cost as little as $200 while still being effective. If you want to install a system yourself without the help of a landscape contractor, keep these tips in mind.

1.  A typical graywater system consists of the following:

  • A three-way diverter valve (as pictured) which diverts water to a sewer or irrigation system.
  • A treatment facility such as a sand filter, and a bilge pump to keep your water clean.
  • A holding tank which cools the water and temporarily keeps it from the drain hose
  • An irrigation system.

2.  You must determine if you have enough land to install a system. State guidelines state that there must be minimal to no contact between homeowners and grey water, which requires the area of water released to be covered with at least 2 inches of rock or mulch. Generally, if your home is located on a lot of a quarter acre or larger, with some buffer space between you and your neighbors and/or a yard, you should have a good chance of meeting the specs

3.  Your system must release water to an irrigation field or a sewer.

4.  You cannot use your grey water system to nourish root vegetables like carrots and turnips.

5.  After designing your grey water system, you must submit the design plan for review and approval by building inspectors adhering to proper standards.

6.  After approval, you can install your system. Upon completion, it must be checked by an inspector.

For more information about

Installing a grey water-reuse system

Newly Revised grey water laws


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