Using Gray Water
"Gray water" refers to household cleaning water harvested for use on plants. Typical sources are the water you have used for bathing, washing dishes and washing clothes.
If you intend to use gray water on plants, you must take care to use appropriate cleaners for bathing, washing dishes and washing clothes. Use low phosphate soaps and avoid bleaches or other cleaning agents. For the long-term health of your soil, alternate waterings between gray water and potable water or collected rainwater. Fertilize your soil with micro-biologically active agents such as organic compost and composted manure to break down unwanted chemical agents in the gray water.
Use Your Shower Water
Place a bucket or pan on your shower floor to collect water. After showering, empty the bucket into a larger container like a large plastic trash can. Then fill your watering can from the large container.
Or, plug your tub drain and bail the water out after showering. You can also pump the water out to a collection reservoir (barrel) using a swamp cooler pump and hose.
Use Your Dishwashing Water
Use a plastic tub set in your sink to wash and rinse dishes then empty it onto your plants or into a collection reservoir.
Use Your Washing Machine Water
Extend the drain hose from your washing machine to a collection reservoir. Take water as needed from the tank.
Or, direct your drain hose into a bucket and carry the full bucket to your plants. Be sure the bucket is big enough and monitor the drain cycle to avoid overflowing.
Install a Whole House System
Check applicable state and local building codes for the handling of gray water discharge. A plumber or a consultant with the appropriate qualifications should engineer your system.
A gray water system can be built into your house during construction or added to an existing home with accessible plumbing (as in a crawl space). These systems usually consist of an underground tank, a pump and separate drain lines from the bath, shower, kitchen sinks and washing machine.
Gray water systems often employ an automatic pump and float switch so that the collection tank is automatically evacuated to the outdoor watering system whenever the tank's water level gets to a set point. On-demand systems use a manual switch or timer to control watering times.