Tips and Uses for Treating Gray Water

Since Adam and Eve left the garden, mankind has been faced with the problem of what to do with waste. Early civilizations would toss their dishwater outside the camp or perhaps use it to put out the cooking fire. As men gathered in larger groups more care had to be used to dispose of their wash water. When I lived in Thailand, I saw people toss their waste into the open sewer in front of their house and then it was flushed out to the Mekong River. However, as technology progressed, better methods had to be found for waste disposal. Today sewer systems are taken for granted as people turn on the faucet and water flows down the drain.

Perhaps you saw our An American Homestead video on composting, in which we dealt with kitchen scraps, animal waste, and human waste. However, we did not discuss what we do with our gray water waste. Gray water is what comes from the kitchen sink, bathroom sink, and bathtub. The washing machine waste water would also be considered gray water. We do not have a washing machine, but if we do laundry by hand in the house, the water is discarded down the bathtub drain.

Our manufactured home came complete with plumbing drain pipes from each fixture. We just had to tie them together into one common drain line. The problem was what to do with the waste water? Shortly after we moved into our home we drained the gray water into a shallow trench along the side of the house, but the waste soon became a smelly mess of soap scum and other partials. It became a priority to move the waste water away from the house in order to maintain sanitary conditions. The answer is a grease interceptor also known as a grease trap. The one we purchased is pictured here. It is made by Endura.


Grease traps have been used since the early 1800s, although the first patent was not obtained until much later. They are a tried and tested method to trap grease, soap, sludge, oil, and small food particles from waste water. The down side is that they must be cleaned several times a year and it is a really messy and stinky job.

persimmon-treesWe looked at several types of grease interceptors including one we could make ourselves. We chose to purchase a pre-assembled unit with a capacity of seven to ten gallons complete with a flow regulator. From each drain, we have an inch and a half drain to the inlet side of the grease trap with a two inch drain line from the outlet side. We have chosen to drain the treated water away from the house, about 75 feet into a grove of persimmon trees. Other usages could be to use the water for a garden or water landscaping, but it would depend on your collection system.

grease-trap2The Grease Trap worked great until the first hard freeze. The first thing to freeze was the flow regulator so water backed up to every sink and froze, and then the grease trap froze. The drains stayed frozen for two weeks. It was very inconvenient because all the waste water had to be carried outside by hand. Lesson learned – a grease trap will not work outside in the winter.

A few design changes were necessary. We eliminated the flow regulator and replaced it with a two inch valve. Secondly, we made a bypass pipe around the grease trap. This allows us to close the valve to the grease trap and open the valve to the bypass. The grease trap will probably still freeze, but waste water should still flow to the drain pipe and away from the house. Thirdly, we will insulate the trap and the pipes. (The grease trap was uncovered for the picture). We will see what happens this coming winter, but we are hoping for the best.

All-in-all the grease interceptor works well. Soap and sludge is trapped inside and clean water flows into the persimmon trees. It is a great solution to dispose of gray water without the need for an expensive septic system.

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About Tim L

After their retirement, Tim and his wife Joann moved along with his daughter, son-in-law, and two grandsons to the American Ozark Mountains to build an off-grid homestead.

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  1. What would you suggest if you lived in Maine where we get months of freezing weather? Would this system even be doable??

    • Kelly, We bypass the grease trap during the winter by closing one valve and opening another valve because the trap will freeze. As long as you do not have standing water in your drains the pipes will not freeze. You just will not be able to use the trap in the winter. Thanks for asking.

  2. Hi Tim, curious to hear how this held up through the 2014-2015 winter season for you all. Thanks

    • The bypass I installed work well and the pipes did not freeze at all last winter. I close the grease trap before the first freeze. Thanks for asking

  3. What is the effect on your trees and the land when you bypass the grease trap?

    • The grease trap is currently bypassed for the winter. There is soap residue that collects at the end of the drain pipe, but there does not seem to be any adverse effect of the stand of persimmon trees that are close by. Thanks, Tim

  4. Tim,

    Thank you for the post. My family and I are moving out of the city and to our cabin in the pacific north west woods. The 750 SQFT house is not plumbed and the land is so wet I doubt a conventional septic system would be effective. The grey water system I have been thinking about sounds very similar to yours. After having your grey water system for several years now is there anything you have or will change or wish you had done differently?
    Looking forward to reading more of your blog.


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