Graywater Reuse

What is Graywater Reuse?

Traditionally, wastewater from your home flows either into your city's centralized wastewater collection system or into your own septic system if you live in an area without access to a centralized sanitary sewer system. Over the years, the definition of "wastewater" in the international plumbing code has been divided into two categories, blackwater and graywater.

Graywater is defined as wastewater from bathroom lavatories, bathtubs and showers, and clothes washing machines. Therefore, blackwater is defined as wastewater from toilets, kitchen sinks, and dishwashers. These are the common definitions set forth by the international plumbing code which is the approved code for many cities across the US. In comparison, graywater is relatively clean and does not have the same treatment requirements as blackwater does. Creating these separate definitions now allows the use of graywater as a water conservation opportunity since graywater does not have to be directed to the sanitary sewer or septic system like blackwater does.

In 1992, Texas passed a law allowing water from clothes washing machines to be classified as graywater. TCEQ has recently passed the proposed changes to the Texas Administrative Code Section 210 (Use of Reclaimed Water) to allow water from showers, bathtubs, bathroom lavatories and clothes washing machines to be called graywater.

On a large scale, municipalities across the United States are starting to implement water reuse programs which is reusing wastewater treatment plant effluent for non-potable purposes such as the landscape irrigation or cooling water. This water is called "reclaimed water" and should not be confused with graywater. These two water sources are completely different. At this time, you will mostly see reclaimed water systems supplying large users of water such as golf courses and power plants.

Even though graywater reuse is not allowed in all states, we believe that graywater recovery will grow and become legal as more states begin to content with water supply issues.

What are the benefits of graywater reuse?

• You have already paid for the water
• It only needs a minimal amount of treatment (in comparison to black water)
• You will offset the use of potable water for landscape irrigation
• You can keep a consistent soil moisture level around your home's concrete slab which may help to prevent the movement and cracking of your slab

How can I use graywater?

Graywater recovery systems allow you to reuse water to irrigate your lawn and landscape plants, used around the foundation of your house to minimize foundation movement, and/or be used in your toilets. This will help you save money on your water bills. Unlike rain, graywater is a constant and reliable source of water that should be harnessed. You pay for water once when it passes your water meter, why not use it as many times as possible.

How much graywater does my home produce?

The chart below shows the percentages of the various components of typical household water use. From this data, one can see that approximately 40% of the water that is used in a typical household can now be used as graywater. On average, a family of four, uses 300 gallons of water a day. 120 gallons of this 300 gallons can now be used in the ways decribed above. These 120 gallons can offset the amount of water needed to water your lawn and landscaping.

The categories in the lower portion of the pie chart from "Bath" to "Shower" are all considered graywater in the states that currently have graywater laws. As you can see, this amounts to approximately 56% of your indoor water use. Imagine reusing this graywater on your landscaping rather than paying for treated municipal to water your landscaping.

Is graywater reuse the future of water conservation?

We believe graywater reuse will become a larger piece of the water conservation discussions as we move forward with the pressures on our local water resources. At this point, only a handful of states approve the use of graywater in or around your home. As pressures increase on our water resources, other states will join the effort. Our graywater regulations center can help your keep current on graywater regulations in your own state.

Go to the next step: How to Reuse Graywater