Bath water Graywater

In 2009 we started a remodel of the bathroom off of our bedroom. The house was built in an era when sunken tubs were in fashion, so our goal was to fill in the sunken part and put in a low water use toilet. Ellen got the idea that as part of the replumbing we could install a graywater option. The plumbing was only slightly more complex, with an alternate path leading toward the outside wall and shutoff valves in both the sewer and graywater directions.
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Outside preparation started with digging 8 inch deep ditches where the drain pipes would go. In the upper photo one can see the white flexible pipe as it emerges from the wall. This will deliver the graywater to a holding tank / distribution “box”. From the tank will be pipes fanning out to moisten the soil in a rectangle near by, and then a long run of a single pipe farther up the side yard.The lower photo shows a longer view which includes the long run by the grapes that are growing along the wall.The idea is to have a small garden near the bathroom, but still have some of the water feed the grapes.
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The pipes are 1 1/2 inch black ABS pipes (we had some from a prior experiment). They were drilled with holes every 10-12 inches to let the water out, and we covered the pipes with weed cloth we had sitting around. The covering with cloth is intended to keep the soil from blocking the holes. Will see if that works.

We thought we would need a holding tank because the volume of the ABS pipes were about 5 gallons, and if we took back to back showers, that would not be enough capacity. (I suppose we could have let it back up in the tub…)
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For the holding tank we settled on a 30 gallon plastic drum (arizonabarrels.com – $18).┬áIt has two bung holes – the top is the graywater input and the bottom has some glued pipes and fittings to the deliver the water via a couple routes to the drain field. The barrel is tilted slightly so less water sits in the bottom.The connections around the barrel are glued to keep them secure. The others are not — since we are not sure what to expect, we may have to dig them up and rearrange things, and a little leakage now is not a problem since we want the water to leak out.
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graywater, part two

After several months of taking showers and seeing how it drained, and how it fed the plants, we decided to dig it up and make some adjustments. Here are some of the lessons learned:

  • For us in central Arizona, 8 inches deep was too deep. The young seedlings were not able to access the water that deep. It did not wick up to the surface because of the depth and the quality of the soil. In the summer, seedlings did not have a chance in the heat without water.
  • There were a few spots in the drainage pipe where the water came out, but it did not come out evenly along the run of the pipe.
  • The long run of pipe originally installed was way more than necessary. The three links of pipe covering about a 4×9 foot area would be sufficient to drain shower water for two people, especially with a holding tank. I did not need that extra 20 feet running along the grapes.

To address these issues, I dug down to the pipes and raised them a couple inches, surrounded them with river rock and covered the rock with hardware cloth as a way to slow down dirt filling in the gravel. The idea is the water would be closer to the surface and flow along the trench better.