Gray Water Cleaning

by Mark Vallet; Updated September 26, 2017

Recycling gray water can be a simple way to lower water usage and help the environment. Cleaning gray water to potable is beyond the scope of most household systems but recycling gray water for garden watering or toilet flushing can be simple and inexpensive.

What is Gray Water?

Waste water that is created from activities like dish washing, bathing and laundry is referred to as gray water. Gray water is cloudy in color. It falls in between fresh water and black or dirty water. Gray water makes up 60 to 80 percent of all waste water created by households. Water that comes from toilets and is contaminated with sewage is called black water.

Cost of Cleaning Gray Water

The cost of cleaning gray water to a potable level on a individual level is cost prohibitive using existing technology. Gray water must be run through an intensive treatment to be made suitable for drinking and this is extremely expensive. Gray water can be recycled for use in gardens or irrigation and is often reused in third world countries where enforcement of purification laws is often non-existent or rarely enforced.

Recycling Gray Water

Gray water can be recycled if a separate plumbing system from the one that handles sewage or black water is used. Using stages of filtration and microbial digestion can clean gray water enough to be used for watering gardens or flushing toilets. A recycling system pumps gray water from a sink or dishwasher into a tank where it is stored until it is used to flush a toilet or water a garden or yard.

Recycling without Purification

There are a number of different ways to recycle gray water without purifying it. The easiest way is to just divert the water directly to the garden or lawn. Ordinances vary by state and county so check with local authorities before installing a system. Diversion systems can be simple such as running a hose from the washing machine to a garden or they can be quite sophisticated and built into a plumbing system. The more complicated systems often use a sump pump and storage tanks. Shower and bath water is best for the garden, if using laundry water it is important to check phosphate and salt levels.

Purification of Gray Water

In order to filter gray water to become potable or close to potable, there are a few different systems to choose from. Mechanical systems such as UV radiation or lava and sand filtration are common examples. Biological systems include treatment ponds, activated sludge systems and constructed wetlands. All of these systems are complicated and normally cost prohibitive for homeowners.

Benefits of Gray Water Recycling

Recycling gray water provides a number of benefits to the environment. It lowers the use of fresh water, reducing the energy usage of treatment plants, and it provides nutrients back to the soil. Installing a simple recycling system can lower your water bill as well.

About the Author

Mark Vallet is a a stay-at-home dad who began freelance writing in 2009. He has produced online content for Demand Studios, and He has traveled extensively within the U.S. and internationally. Vallet holds a Bachelor of Arts in English literature from the University of Iowa.