Every time you take a shower, brush your teeth or do a load of laundry, you're letting water — one of Earth's most precious resources — swirl down the drain. Instead, what if you reclaimed that water and reused it to flush toilets and water the flowers?

Some municipalities, home builders and water-recycling manufacturers are increasingly making that a viable option. In the United States, where the average household uses more than 300 gallons of water a day, one of the greatest untapped resources is greywater. That's the water that drains from bathroom showers, tubs and sinks, as well as from washing machines. Recycling this discharge won't make it suitable as drinking water, but it can be reused in many ways, cutting a home's overall water usage by as much as 40% by some estimates.

But achieving that goal isn't so easy: Greywater recycling isn't allowed in many municipalities, and those that do have detailed ordinances to ensure that it's handled safely and won't contaminate the main water lines. What's more, installing a greywater system in an existing home may involve tearing out drywall and replumbing fixtures, which is both messy and costly.

"In many cases, if you do any major work to your plumbing system, it requires a permit and has to be done by a licensed plumber," said Bob Rubin, an emeritus professor at North Carolina State University and expert in biological and agricultural engineering. "Several greywater systems on the market have electrical connections that have to be made for the filters and controls," he adds.

Compelled by a looming water crisis, Tucson, Ariz., is one of a handful of major U.S. cities that mandates builders to include piping for greywater recycling in new homes. In 2019, the city took part in a pilot program with Lennar Homes to install greywater filtration systems in some homes in two new subdivisions. At no additional cost to the owners, new homes could be equipped with a greywater filtration unit made by Greyter Water Systems that would treat water captured from showers and bathtubs to a near-potable quality for reuse in toilet flushing. That alone reduces indoor water consumption by about 25%, says John Bell, chief commercial officer at Greyter, based in Ontario.

Sarah Almand and her husband opted to include a Greyter system when they purchased a new house in one of the subdivisions for $330,000 in 2019. "I had never heard of a greywater system, but I was really interested," says Almand, 43, whose family includes two young children. "I like to help out the environment, especially in Arizona, where water is scarce."

The filtration unit, in the garage, measures about 2 feet by 2 feet, Almand estimates. Water is captured from the house's showers and bathtubs and runs through a series of filters before it's returned to toilet tanks for flushing. The recycled greywater looks and smells no different from their tap water, she adds. And because the recycled water is used just for toilet flushing and not for landscaping, she's not required to use special shampoos, soaps and cleaning supplies to protect grass, trees and plants. As part of its agreement with Tucson Water, Greyter monitors and maintains the system at no extra charge for five years.

Financial incentives increase the likelihood that builders and homeowners will install greywater systems, says Kevin Reidy, senior state water-efficiency specialist with the Colorado Water Conservation Board. In Denver, a $130,000 grant from the conservation board is enabling Greyter to install greywater systems in 25 new Lennar Homes at no additional cost to the owners.

Another Colorado city, Castle Rock, gives builders a 33% discount on the tap fee — the charge to hook homes up to the city's water supply — if they fall below caps on indoor and outdoor water usage. Programs like these "could pave the way for more incentives to make new developments more efficient," Reidy says. Still, only four Colorado jurisdictions have enacted ordinances so far, Reidy says, which might be holding back widespread use. Some cities are slow to act because they lack the resources to issue permits and conduct inspections.

There are several ways to recycle greywater, the simplest being to capture water in a container before it reaches the drain and carry it outside. Rubin uses this method in the summer to water the flowerbeds in his yard.

Basic systems use the force of gravity and/or an electric pump to take water discharged from clothes washers and divert it to outdoor irrigation lines. Materials typically cost between $150 and $300, and labor ranges from $500 to $2,000, depending on the scope of the work, according to Sustainable Solano, a nonprofit conservation group in Benicia, Calif. The state allows laundry-to-landscape setups in single-family houses without a permit as long as certain guidelines are followed.

Sustainable Solano helped Jonathan Gómez and Edlin Símental add a laundry-to-landscaping setup in their Suisun City, Calif., home in November. The couple, both 28, purchased their fixer-upper for $330,000 early last year with the goal of making it more eco-friendly. "We wanted to be more sustainable and self-reliant," says Simental, a training facilitator. "We can find ways to be not so wasteful."

The system requires very little oversight, says Gómez, who repairs electronics. "Every now and then, I check the hoses and make sure nothing is plugged up. So far, the installation has gone pretty seamlessly. It's low maintenance — everything is buried and underground," he says.

Compelled by droughts in California and in her family's native India, Shreya Ramachandran launched a nonprofit foundation called the Grey Water Project in 2016 to promote greywater recycling. The following year, when she was in eighth grade, Ramachandran persuaded her parents to help her install a laundry-to-landscaping system in their Fremont, Calif., home.

"It's such an essential drought solution and something we should all be doing more of," says Ramachandran, now an 18-year-old freshman at Stanford University.

A number of companies make more elaborate greywater recycling systems that can filter discharged water and, when necessary, store it briefly in a holding tank before use in irrigation. Water Wise Group Inc., a wholesale distributor based in Paso Robles, Calif., makes a unit that sells for $729 plus shipping. Installation costs vary, depending on whether the home has a basement or crawl space for easy access to plumbing, says Remy Sabiani, founder of Water Wise Group.

Reducing overall water consumption is the main reason customers install a Water Wise unit, Sabiani says. But many of his rural clients cite an added benefit: The system diverts greywater — up to 40,000 gallons a year — away from their septic systems. "Your [septic] tank may be too small for the amount of water that goes into it. Replacing it with a bigger tank can easily cost $15,000." A Water Wise system spares homeowners that expense, he says.

But even bathroom shower and sink water contains microbial matter, so greywater systems shouldn't store the discharge in tanks for long periods of time, he adds. This is also why untreated greywater shouldn't be used for sprinklers or washing the car — the aerosol makes the pathogens airborne.

"I believe firmly that people should follow their [city] code," Rubin says. "All too often, things get installed without going through building officials. Don't be a greywater guerrilla."