By Kim Robson:
What Is Grey water?
Grey water is the wastewater from shower drains, baths, sinks and washing machines. Unlike black water, which is sewage from the toilet, grey water can be used for watering houseplants, landscaping, or even flushing the toilet; so it’s a recyclable resource. Instead of flushing grey water away as sewage, we can manually divert or capture it, reducing stress on precious potable water supplies, lowering home water usage and costs, and supporting a garden or landscape.
With the extended drought conditions across the western U.S. and throughout the world, we need to reduce the overall demand for fresh water through water-wise landscaping, rainwater harvesting, water-efficient appliances and fixtures, and embracing unconventional methods of wastewater recycling and reclamation.
Rules and regulations about grey water reuse can vary dramatically depending on your municipality. In addition, improper management of grey water can lead to odor, pests, or pathogen issues, so it’s critical that you do thorough research before installing any grey water system.
Not all grey water is alike. Water from the kitchen sink or dishwasher can contain bits of organic matter and soap residue. It can harbor pathogens; in fact, kitchen sink water is classified as black water under some codes. But bathroom sink or tub water is often much cleaner. However, with the proper system, such as a biofilter or mulched basin, grey water from the kitchen sink can be used.
Catch Your Warm-Up Water
Warm-up water is the water that goes down the drain while you’re waiting for the hot water to reach the tap. There can be quite a lot if your water heater is located far away from the point of use. To capture warm-up water, simply place a bucket or large bowl under the faucet when you turn on the hot water, and remove it when the water is hot. Because it’s perfectly clean, warm-up water can be used to directly water herbs or vegetables intended for consumption.
How to Reuse Grey Water from Bathroom Sinks
Unless you re-plumb your sink drain into a grey water system (check your local building and health codes), you’ll need to manually bail out full sinks into buckets, or remove the J-trap from beneath the sink and replace it with a bucket. If you go the bucket route, you’ll need to be diligent about checking the water level so it doesn’t overflow. This grey water can be used to flush the toilet (pour it into the bowl, not the toilet tank) or to water outdoor plants or trees, as long as no harsh detergents were used.
How To Reuse Grey Water from the Bathtub
If you are serious, some plumbing work to install a 3-way valve might be in order. Drain water can be diverted either to a grey water system or directly into the sewer line, which can be good if you have periods of high water use that would overload a small grey water landscape system. If re-plumbing your house isn’t an option, you still can reuse water from showers. Just plug the drain and let the bathtub fill up, then use a bucket to manually bail out the bathtub.
How to Reuse Grey Water from the Laundry
If you don’t use harsh laundry detergent or chlorine bleach in your washing machine (which you shouldn’t do), a laundry-to-landscape grey water system can water trees and landscaping. Remove the washing machine’s discharge hose from the house drain, connect it to a length of hose that can reach your yard, and you can reuse grey water every time you do the laundry. If you don’t want a bog in your yard from always discharging water in the same place, you’ll want to move the hose to a different spot with each load of laundry. Oasis Design has a better method and a lot of other great info on grey water implementation:
Large-Scale Grey Water Systems
If you’d like to install a large-scale grey water system at your home, be sure to thoroughly evaluate your options, consult with a grey water professional, and find a system that complies with local regulations, and is appropriate for your needs and your landscape.
In the video below, Trathen Heckman of Peak Moment shows how to make a safe, ecological and legal suburban home grey water system. Follow the water as it drains from the bathroom tub and sink and laundry through a unique valve leading into the backyard garden. The water is then piped below ground to several destinations in the yard, where it supplies water for plants. It also can flow into an optional wetland and underground pond for filtering. Trathen discusses dealing with local government agencies, system design and construction (including pictures), costs, and resource books.