This is a low-tech system that provides easy distribution of greywater to many plants. It is relatively low cost, and easy to install. The washing machine's internal pump slightly pressurizes the greywater, so this system can irrigate plants that are slightly uphill or further away along flat ground.
The washer hose is connected to a 3-way valve that can divert greywater either to the sewer or the greywater system and piped outside with 1” rigid pipe, like PVC. This system requires 1" diameter tubing/pipe- larger diameter tubing will decrease the pressure and make it harder to spread out the water; and smaller diameter tubing will add too much strain on the pump. Outside 1" poly or HDPE (black plastic tubing) is connected to the rigid pipe and "barbed" Tee fittings split the flow and allow greywater to spread out and water many plants.
For step-by-step instructions on how to build this system, download the San Francisco Public Utility Commission's manual here.
• Greywater can travel slightly uphill or longer distances across flat yards.
• Accessible 3-way valve makes it easy to switch between the greywater system and the sewer/septic.
•Very little maintenance.
*Very little digging required.
•Easy to spread out water and reach many plants
•Easy to regulate amount of water plants receive
•Flexible- Easy to change after installation
• Involves some very minor plumbing rerouting.
•If poorly designed the system could add strain on washer pump and potentially shorten its life.
•Some parts not readily available and must be ordered.
Kits available from Clean Water Components
•1" brass three-way valve
• 1" PVC pipe and fittings
•"auto vent" or check valve used for air gap
•If yard is higher than washer, use a swing check valve
•1" HDPE (black polyethylene plastic) tubing and barbed fittings
• Ball valves (1" and 1/2")
1" HDPE barbed fittings and tubing are not available in most stores. You can mail order from CleanWater Components.com or try a large irrigation supply store. Some Ewing Irrigation stores (or other large irrigation stores) sell regular 1" tubing that is round and thicker walled and over all easier to work with. Unfortunately they usually come in 500 foot rolls. In areas with agriculture or vineyards, it's possible to find the 1" tubing in 100' sections at a local farm or irrigation store.
Cost: $150-$250 in materials. Labor costs vary, but typically add a between $300-500 to the materials depending on the size and complexity of the system.
To maximize the life of your pump avoid pumping greywater more than a few feet above the rim of the washer. If you are sending greywater long distances over flat ground the friction in the pipe will add some resistance on the pump. A safe rule of thumb distance is 50 feet of horizontal pipe.
Download a printable version of this diagram here.