Water-efficient toilets could potentially save up to 170 billion gallons of water per year across five states facing water scarcity, according to new research from the Alliance for Water Efficiency (AWE) and Plumbing Manufacturers International (PMI).

The study focused on Arizona, California, Colorado, Georgia and Texas, where water shortages are prevalent. The “Saturation Study of Non-Efficient Water Closets in Key States” research found that if non-efficient toilets in residential properties are replaced with water-efficient ones, the five states could save 170 billion gallons of potable water yearly or 465 million gallons saved per day, which is equivalent to up to 360 billion potable gallons of water per year saved nationally.

More than 13 million non-efficient toilets, defined as ones with gallons per flush (gpf) of more than 1.6 gallons, remain installed in Arizona, California, Colorado, Georgia and Texas residences, and represent about 21% of all toilets installed in these states. As toilet flushing is the largest single indoor use of water, representing 24% of total use in single-family homes, replacing non-efficient toilets in the five states researched would save a significant amount of water overall.

For visualization, savings of 170 billion gallons of water per year equates to:

-Enough water saved to take 10 billion showers – more than one for each person on the planet

-Enough water saved to serve the indoor home water needs of a city of 100,000 for 45 years

-Enough water saved to fill 250,000 Olympic-sized swimming pools

-Enough water saved to fill 1,000 Rose Bowls

-Enough water saved to equal the water that goes over Niagara Falls in 2 1/2 days

At the current 4% annual toilet replacement rate in the U.S., the potential savings illustrated in this study will not occur for another 15 to 30 years unless replacement programs are accelerated.

“This study affirms the important and sometimes overlooked role that water-efficient plumbing products – and programs such as the EPA WaterSense label – play in assuring water sustainability for our nation,” said Mary Ann Dickinson, AWE president and CEO in a news release. “We are nowhere near the potential of water savings we can achieve through water efficiency.”