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Backyard Graywater System
From MAKE Magazine
This project first appeared on the pages of MAKE magazine.
Get a lush garden from your laundry water.
- Author: Tim Drew
- Time required: 1 weekend
- Difficulty: Moderate
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The typical American household sends the water it's bathed, brushed its teeth, and cleaned its clothes with, called graywater, to the municipal waste facility. Then it waters its lawns and gardens with more fresh water, wasting about 1,000 gallons per month. But you can safely use graywater for irrigation if it's handled by a proper recycling system, and if you use biodegradable detergent and don't wash diapers.
As an avid gardener living in dry California, I wanted a simple and inexpensive way to reuse water to keep my garden green and healthy. In 2004, my wife and I had to retrofit our house's basement, so I moved the laundry machines to the back carport, which is at a slightly higher elevation than our adjacent garden and far from a sewer connection. This was my opportunity. At first, I simply let waste water from the washer run into a 3" flexible corrugated pipe, which I moved around to drain near any plants that I wanted to water. Later, after we decided not to move the machines back inside, I built this more permanent underground system.
Sections
- Install the standpipe and underground drain pipe.
- Split the line with a double-ell fitting.
- Install the outlet pots.
- Bury the pipes.
- Graywater Systems: A Gray Legal Area
Tools
- Drill, with large drill bit, 1/2" to 1"
- Hacksaw
- Shovels
- Tinsnips
- Torpedo level
- Wheelbarrow
Relevant parts
- ABS pipe, 2" long enough to run from the washing machine down underground and to irrigation outlets
Relevant parts (continued)
- ABS primer
- Glue, for ABS
- ABS fittings, 2" to connect pipe; I used 90° elbows, 16° elbows, and straight junctions.
- ABS fittings, 2" double-ell, 1 for each split I used only one. You might need to get these from a professional plumbing supplier; all other materials should be found at a local hardware store.
- Plastic pot, 5 gallon or 10 gallon 1 for each split and irrigation outlet. I used 3.
- Stepping stones, Concrete or pavers
- Bark mulch, Western red cedar, medium chip $1-$4 per cubic foot
- View:
- Paginated
- Full width
Edit Step 1
— Install the standpipe and underground drain pipe.
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My design uses a 2" ABS standpipe that runs down from the washer and connects to a gently sloping horizontal pipe buried under a garden path. At the other end, the water splits and travels a bit farther in 2 directions, then flows out through perforated pots and bark chip mulch, and into the soil beneath some water-loving plants and trees. The area to be watered was 40' away and 10' below the washer.
First I excavated the path that the underground pipe would follow, making sure that it was deep enough to allow for a downward slope of at least 1/4" per foot. I installed the standpipe behind the washer using pipe straps, and joined it to the underground pipe (as with all joints) using ABS primer and glue. Later, I buried the joint in gravel.
Edit Step 2
— Split the line with a double-ell fitting.
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At the other end of the long underground pipe, I installed a double-ell fitting to split the water into 2 streams feeding different locations. To make sure the water split evenly, I held a torpedo level against the fitting to ensure it stayed level while I glued it up. To keep the fitting easily inspectable and accessible for repairs rather than buried in dirt, I enclosed it in a plastic pot .
Edit Step 3
— Install the outlet pots.
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I dug trenches for more 2" pipe to run from the split to the 2 outlets where the water enters the soil. At each, I used a perforated 5gal black plastic pot to distribute the water. I used tinsnips to cut a hole high up on the side of each pot for the pipe to enter, and drilled 1/2" to 1" perforations in the bottom and around the sides for the water to flow out. You can also nest a perforated 5gal pot below a 10gal pot used as a retaining wall.
I buried the pots in trenches dug 3'-4' long and 1'-2' deep, filled the trenches back up with medium chip bark mulch, and covered each pot with a paving stone. For more height, you can also cover with a trimmed inverted pot. The mulch helps distribute the water to the plant roots while maintaining good drainage around the outlets.
Edit Step 4
— Bury the pipes.
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Finally, I buried the pipes, covering the main pipe run with paving stones and redwood bark mulch to turn it back into a path. I also put a paver over the split point, to allow for easy access later.
TIPS: It's important to keep an open space around all the pipe terminals, to let you periodically remove any solids, so they don't build up and block the flow. Similarly, it's important to have an open space around the double-ell, so the split can be inspected. Other systems I've seen have a large hole bored into the top of the double-ell to let you visually inspect the interior of the fitting for clogs and clear it out with a finger if needed.
Edit Step 5
— Graywater Systems: A Gray Legal Area
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CAUTION: Graywater systems are legal in California and other states, but depending on your location, you might be legally limited to certain types of systems and required to get a permit.
Obtaining a permit can be a roll of the dice, and many people don't bother because of the expense, hassle, and uncertainty. This creates a Catch-22 situation: local building inspectors are overly cautious and scrupulous because they have little familiarity with graywater recycling, so nobody builds permitted systems and the inspectors stay in the dark. The more graywater systems people build with permits, the more experience building inspectors will have with them, and the easier it will be to build them and get inspectors to sign off on them.
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