COLLEGE STATION – When the weather turns dry, Texans may start thinking about the best ways to avoid high water bills and still maintain their landscaping. Gray water may be one option, said Dr. Bruce Lesikar, Texas Cooperative Extension agricultural engineer.
Gray water is the water that has passed through showers, sinks, bathtubs or washing machines, Lesikar said. It makes up about half of the water used in the home and normally passes into onsite wastewater treatment systems or city sewer systems.
"The typical resident will have about 30 gallons per person per day," he said. Gray water is a source (of water) that's already paid for, and you can use it in your landscape."
It is different from black water that comes from the toilet or kitchen sink. Black water has the potential to have many solids and therefore cannot be used on landscapes without treatment, he said.
Gray water is not without risk, though. It may contain high concentrations of sodium and phosphorus from soaps, detergents and cleaning products, which aren't good for plants.
"It does come into contact with the human body so there is a risk for having organic matter as well as pathogens," Lesikar said. "So it needs to be used safely and wisely."
State regulations affect how gray water systems may be installed and used, Lesikar said. A typical gray water system consists of a diversion valve to direct gray water to the reuse system, a tank to separate solids, an effluent screen to trap solids before they leave the tank, an overflow pipe with two black-water valves going to the onsite wastewater treatment system or municipal sewer, and a distribution system delivering gray water to the plants. The pipe for distributing the water must be purple to designate that it is reclaimed wastewater.
Typically, gray-water systems that are whole-house systems are completed at the time the house are built.
"If you are planning on a gray-water system, you have to start by planning early," he said. "Houses that are on blocks or above the ground do have the ability to be re-plumbed to separate gray water for use. For houses that are on slabs, it is more difficult to separate the sources once the house is built."
If washing machines or other sources are on exterior walls, however, homeowners can plumb through the wall and access that water, he said. However, the gray-water tank must be able to overflow through two back water valves to the onsite wastewater treatment system or municipal sewer to be in compliance with state regulations.
