With water in short supply in many locales in the United States, recycling grey water can help reduce water consumption. While you need clean water for kitchen use, laundry and personal hygiene, you can recycle water with some soap and other impurities. Such grey water is safe for outdoor use such as irrigating gardens and lawns, and for indoor use such as flushing toilets. Simple grey water recycling systems are easy and inexpensive to install.
Identify the pipes coming from the drains of your showers, baths, bathroom sinks and washing machine. Find a location where you can access the pipes before they join the main stack or the pipes coming from toilets.
Cut or unscrew the drain pipes, depending on your installation. Install plugs on the lower pipes. Connect new pipes to the upper pipes coming from the showers, baths and sinks to collect the grey water. Drill holes to run the pipes inside walls and through floors if you want to collect the grey water in your basement or crawl space. Fasten the new pipes securely to wooden supports in the walls and floors.
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Link all the pipes to a common drain pipe in the basement or crawl space. If you are planning to use the water for gravity-fed irrigation, make sure you install the pipes along the ceiling of the basement, always above the outside ground level. If you don't have a basement or crawl space, or it is too low, run the common drain pipe directly outside. If you live in an apartment or condo, you can recycle grey water by installing a short length of pipe under sinks and having it drain into a bucket. You can use the bucket to flush toilets.
Install a storage tank if you want your irrigation to extend over longer periods of time. Run your main grey water drain pipe to the storage tank. If you don't need storage, run the pipe directly to your garden; otherwise, run a pipe from the storage tank to the garden and install a valve to control the flow.
Place the storage tank indoors if you are in an area with frost in the winter. An indoor storage tank must be closed, with a vent to the outside. If your system is gravity-fed, install the storage tank above the outside ground level. Don't store the grey water for more than 24 hours because bacteria may grow and the water may develop a smell.
Install a diversion pipe from the storage tank or from your grey water drain pipe into your main drain and the sewers or septic tank. Install a valve to allow you to divert the grey water when you can't recycle it, for example if the ground in your garden is frozen.
Test your system by running a bathroom tap and checking that your gravity-fed irrigation system works, your storage tank fills up and empties, and your diversion pipe functions as planned.
Install a pump in the storage tank if you want to use your grey water above the level of the storage tank or if you need pressure for a hose. Use a pump designed for pumping grey water or effluent to avoid having it blocked by particles in the water.
Run a hose or pipe from the pump outlet up to where you need the grey water. Use such a system to fill buckets for flushing toilets or watering cans for additional irrigation. Flush toilets by pouring grey water into the bowl to avoid damage to the tank flushing mechanism and possible contamination of your water supply.
Systems with a storage tank and pump need maintenance and frequent cleaning to remove debris from pump filters and flush the storage tank with clean water.
The smell from grey water that is stored too long is the result of bacteria build-up. Don't recycle such grey water.