Every day, the average American family of four uses about 400 gallons of water for things like washing dishes and clothes, bathing, brushing their teeth, and flushing toilets, according to the U.S. Environmental Protection Agency’s WaterSense program. About half of that—the water from tubs and showers, bathroom sinks, and loads of laundry that don’t include dirty diapers—is considered greywater. It can’t be used again for drinking water, but it can be recycled for other purposes, such as flushing toilets and irrigation.
Active greywater systems capture drain water from showers, tubs, and washing machines and direct it to a holding tank, where it’s filtered and then pumped back to flush toilets. Some of the benefits of greywater recycling include reducing the demand for fresh water and relieving strain on water treatment or septic systems. If you live in a part of the country that gets little rainfall, greywater recycling can be a way to maximize water savings.
Toilets are ideal for greywater usage: They’re the biggest source of water consumption in the house, accounting for nearly 30% of an average home’s indoor water use, according to the EPA. The average U.S. family spends about $500 a year on its water and sewer bill, so savings potential is about $150 per year.
If you’re thinking about buying an active greywater system, here are some things to consider:
Cost of active greywater systems
A residential greywater system runs $1,900 to $2,800, depending on the tank size, plus the cost of a licensed plumber to run new water supply lines for the toilets and the recommended fresh water bypass and shutoff valve. Some drains may also need to be rerouted. A 2008 University of Colorado study on the system reported a cost of $1,360 for a two-day installation in a new house, plus $14 a year for chemicals and $4 a year worth of electricity—to save $23 a year on water.
Many greywater systems proponents say that while the active systems make sense on an institutional scale, they aren’t efficient at the single-family level.
“Any system which uses a pump, filter, or costs more than you spend on water in a year is suspect,” says Art Ludwig, an environmental systems designer and author of “Create an Oasis with Greywater.”
Are greywater systems legal?
Greywater by definition contains contaminants, and health regulations control greywater systems carefully.
“A lot of municipalities just won’t let you do it,” says Andy Padian, vice president of energy initiatives for the Community Preservation Corporation. “They’re concerned about things like pollution and cleanliness, and so they don’t want you reusing water.”
The legality of greywater systems varies from state to state, says Laura Allen, co-founder of Greywater Action for Sustainable Water Culture, a non-profit collaborative of greywater advocates. “It’s quite challenging in many places.” Not surprisingly, the states that have the most supportive codes are in the more arid parts of the country—Arizona, Texas, and New Mexico.
The need for ongoing maintenance
Another consideration is the effect on your home’s plumbing. Disinfection of the greywater requires a fairly high level of chlorine, which can cause deterioration of toilet flappers, says Tom Bruursema, general manager of the wastewater treatment unit program for NSF International, an independent testing organization for food, water and wastewater.
“That’s a reality of using these systems in the home,” Bruursema says. “They need to consider downstream plumbing issues.”
In addition to the plumbing requirements, active greywater systems need space for both the system and for water storage. Tanks can run over 100 gallons. Maintenance is important, too. Because filtration is a key element of a greywater system, the filters need to be cleaned regularly and chemicals added to the system.
“They’re not install-and-forget,” Bruursema says. “This is probably the most substantial step you can take in terms of water conservation in terms of typical options.”
Less expensive options
Alternatives for those who’ve decided that installing a greywater system makes sense. Among less pricey possibilities:
- A bathroom sink greywater recycling system. The Aqus system installs under the sink and collects and pumps water into that bathroom’s toilet. A kit runs about $350. A skilled do-it-yourselfer with plumbing experience can install it in a few hours. It can save 10 to 20 gallons of water per day in a two-person household, according to its manufacturer, WaterSaver Technologies. The University of Colorado researchers reported an annual water savings of $23 per toilet.
- A sink toilet lid. This is a tank lid with a built-in sink basin and an aerated spout. It attaches to the fresh water intake for the toilet so you can wash your hands or get a drink with fresh water that then goes into the toilet tank for flushing. It’s simple to install and costs about $120. It can save up to two gallons of water per person per day, according to its manufacturer, SinkPositive.