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KEY POINTS
Policies requiring efficient toilets, showerheads, and appliances have driven down indoor water use.
Per person use indoors for single-family homes is 38.5 gallons a day, according to the study.
The biggest residential water savings to come will be outdoor use.
Decades ago, before it was much of a concern, water moved through the average U.S. home in enormous quantities.
Toilets pulled 3.5 gallons per flush or more. Washing machines filled like tiny swimming pools. Water flowed and flowed.
Things have tightened considerably since then.
New data shows that U.S. homes are becoming ever more efficient in their water use.
Between 1999, when the first residential end-use study was released, to the third edition, which was published last week, indoor water use dropped by 43 percent.
The tightening of indoor water use has allowed cities to grow despite mounting concerns about water availability, especially in the western states.
Peter Mayer, who led all three studies, attributes the three-decade decline not to behavioral changes but to federal policies, codes, and standards that required water-efficient designs.
“It’s almost entirely due to technological changes in fixtures and appliances,” said Mayer, principal engineer at Water DM. “There are some behavioral components but they are quite small. The real impact has been the fact that when you flush the toilet it uses much, much less water today than it used to. And when you run a load of clothes, those machines use half the water they used back in the 1990s.”
The main contributors to indoor water use, the study found, are toilets and showers, which combine for about 60 percent of the total. Faucets, which rank third, are another 23 percent.
Per person indoor use, according to data from individual homes, was 38.5 gallons per day for single-family homes and 39.8 gallons for multi-family buildings.
Past and Future Water Use
The catalyst for these water-use changes was the Energy Policy Act of 1992, which was signed into law by President George H.W. Bush. The act dramatically tightened the water-use standards for toilets, showers, and faucets. Later, the Department of Energy mandated that clothes washers use less water. Then in 2006, the EPA launched WaterSense, a voluntary program to label the most water-efficient options available in the marketplace.
The Trump administration has attacked those same path-breaking policies. In a May 2025 executive order calling for the repeal of federal water-efficiency standards, Trump labelled water conservation policies as part of the “unnecessary radical green agenda.”
Water sector representatives see it differently. Conservation has helped cities grow while using less water. In Santa Fe, for instance, water use per person has dropped by 42 percent since the mid-1990s while total water use in the city is the same as the mid-1980s. In the wetter Seattle metro area, water use is about the same today as the 1950s.
“Studies like this can help utilities with planning, conservation, and infrastructure,” said Kenan Ozekin, the chief research officer for the Water Research Foundation, which sponsored the study. The data informs the correct size for treatment plants and how much water might be needed for future growth.
Even with the three-decade decline, there is still room for improvement. The federal standard for toilets is 1.6 gallons per flush. Yet more efficient models are on the market. California and Colorado – two states where water supply is a policy priority – have adopted the WaterSense standard of 1.28 gallons per flush as their own.
Local governments are displaying even more ambition. Castle Rock, a high-growth city on Colorado’s Front Range some 30 miles south of Denver, passed an ordinance last year that all new homes and apartments must install ultra-high efficiency toilets that use 0.8 gallons per flush. The Cambria Community Services District, in southern California, requires high-efficiency appliances and fixtures to be installed when an existing home is sold.
In light of the water-conservation success indoors, the biggest savings to come will be outdoors, Mayer said. In dry western regions, lawn irrigation and landscaping can account for half or more of a city’s water use.
The study drew from several data sources. Forty-eight utilities provided data on residential water use in their service areas. Nearly 60,000 households responded to a water-use survey. And nearly 70,000 in-home readings were provided by Flume, a company that makes a water-use sensor. Because homes with a Flume device might be more attuned to their water use, the researchers attempted to select homes that matched regional consumption patterns.
No study is perfect, but the results show an unmistakable trend line for indoor water use: down.
“It’s important in the context of the Colorado River and the water crisis in America to understand that the residential sector has really been doing its part,” Mayer said. “The residential sector has worked hard and there’s been concerted effort to reduce consumption. And it’s been successful.”
Lead image: U.S. households are using less water thanks to more efficient fixtures and appliances. Photo @ J. Carl Ganter/Circle of Blue
