GRAY WATER IRRIGATION

GRAYWATER IRRIGATION

This article, written by the American Ground Water Trust was originally published in THE AMERICAN WELL OWNER, 2000, Number 4]

USE OF GRAYWATER FOR IRRIGATION

Have you ever thought that diverting shower water to your lawn would be a neat way to recycle water and get a double benefit? Homeowners need to think carefully before diverting wastewater – there are matters of health, economics and law to consider - read on.

Semi-clean wastewater is called "graywater." This includes a home’s wastewater from washing (sinks, bathtubs, clothes and dish washing machines) and food preparation. Wastewater from toilets and garbage disposal units is called “black” water. In most urban areas all household wastewater (gray and black), flows to the public sewer, ending up at a wastewater treatment plant. In rural areas many households have on-site septic systems for wastewater. Most septic systems include a collection tank followed by a leaching area. Solids in the wastewater settle out in the tank and bacteria begin to break down the organic materials in the waste. Excess water passes from the tank out to the leaching area, where it is released into the soil and natural bacterial treatment continues.

There may appear to be advantages in using graywater to water gardens, lawns, and outdoor plants, particularly in areas where water is expensive and scarce. However, for health reasons, careful and diligent maintenance is required for the safe operation of a graywater irrigation system. Graywater can harbor bacteria in the mixture of dirt, soap residues, cleaning agents, food bits, etc. Any standing water left too long can become a breeding ground for more bacteria and other organisms. A system left unchecked could lead to health hazards.

Some general rules for graywater application to minimize potential health risks: ß Apply graywater only through a subsurface irrigation system ß Only apply graywater to non-food plants ß Do not allow the water to pool on the surface

ß Don’t let children or pets play in areas that have been watered by graywater

Using graywater for irrigation usually requires a separate piping system within the home to prevent mixing with the black water. If you divert too much graywater, it can stop the septic system from working properly. The waste piping system will need to be designed with on/off and back-flow prevention valves so that graywater can be diverted back to the sewer or septic when not needed for irrigation. Most commercially available home irrigation equipment is designed only for high quality water and will clog up very quickly if wastewater is used. In many states it is against health code regulations to divert graywater from the sanitary sewer line or an on-site septic system. Before using graywater for irrigation, check with the local building inspectors and health officials. Graywater diversion is not a solution for septic system overload problems.

Most wastewater flushed down the drain is eventually released back into ground water after treatment in a septic system or returned to surface water after extensive treatment at a wastewater treatment plant. Water down the drain is not really wasted! It is just a part of the hydrologic system. If you want to save water, installing water efficient irrigation equipment and practicing water conservation methods in the home may be the best way to go.

You can obtain additional basic information on graywater recycling at: http://www.eren.doe.gov/femp/greenfed/4.0/4_6_graywater_rainwater_har.htm. This is a website maintained by the United States Department of Energy.

[© American Ground Water Trust. This article may be reprinted for non-commercial educational purposes provided it is used in its entirety and that reference is made to its source as an article in THE AMERICAN WELL OWNER, 2000, Number 4]