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Nothing Icky About ‘Toilet-to-Tap': Water Recycling Explained

July 16, 2021, 10:01 AM

Wastewater that recently swirled down a toilet bowl may be coming to your tap, in purified form, especially if you’re in a drought-stricken area where drinking water is increasingly scarce.

More municipal water systems in the West are considering water recycling, known in some places as “toilet-to-tap.” And Congress may begin supporting the idea as water systems scramble to find secure water supplies amid a decades-long drought driven by climate change, which may be the worst the region has experienced in more than a millennium.

Here’s a look at the context for a national discussion about water recycling, how it’s regulated, and what’s at stake.

1. What is water recycling?

It’s the process of purifying and reusing water that has been flushed down the toilet or goes down the drain.

There are three kinds of water recycling:
• Non-potable reuse of wastewater for grass irrigation and industrial uses.
• Indirect potable reuse of treated wastewater that’s sent into rivers or underground to mingle with surface or groundwater, and later purified and used for drinking.
• Direct potable reuse of treated and purified wastewater for drinking.

Indirect potable reuse has been used throughout the country for decades. But direct “flush to faucet” reuse is rare, although accounting for up to 8% of all effluent produced in the U.S., according to the Environmental Protection Agency’s 2017 Potable Reuse Compendium.

A water system in Big Spring, Texas, was one of the first in the U.S. to start directly recycling wastewater in 2013. Today, Southern California is among the largest regions that’s either planning or already using water recycling projects. San Diego expects 40% of its water supply to come from recycled water by 2035.

2. Isn’t drinking (former) toilet water gross?

Maybe in theory, but the reality is recycled water can be even cleaner than most tap water.

Several different technologies exist to filter out waste, pathogens, odors, and other pollutants. Reverse osmosis, for example, uses membranes so tight that only water molecules can pass through, removing minerals, calcium, chlorine, salts, and other solids, according to the San Diego County Water Authority.

“Purified water produced in California with state-of-the-art technologies is higher quality than most bottled water,” the San Diego County Water Authority says on its website.

3. Why are water systems considering it?

Extreme heat and drought in the West, combined with urban growth, are straining already limited water supplies and compounding water availability challenges.

“You see more and more communities running out of options—especially inland communities,” which are pumping their aquifers dry, said Tzahi Y. Cath, a civil and environmental engineering professor at the Colorado School of Mines who is helping Colorado Springs directly recycle its wastewater.

As the West’s drought wears on, utilities can recycle their wastewater directly, helping them tap into a water supply that’s nearly continuously recyclable with minimal loss, Cath said.

Even with drinking water being used to water lawns in some areas, up to 90% of tap water can be recovered through wastewater recycling, Cath noted.

4. What role does government play?

While the EPA doesn’t regulate recycled wastewater, states do have to ensure that all drinking water complies with the federal Clean Water Act and the Safe Drinking Water Act.

Former EPA Administrator Andrew Wheeler released a National Water Reuse Action Plan last year calling for reusing municipal wastewater, stormwater, and water from oil and gas operations.

Few states have developed regulations for direct potable reuse so far. California law requires the California State Water Resources Control Board to adopt water recycling criteria for direct potable reuse by the end of 2023. Florida issued draft rules in May.

In Colorado, where the population of about 5.75 million is expected to double by 2050, the state’s long-term water plan includes wastewater recycling as a major component. The Colorado Department of Public Health and Environment is writing a regulation governing direct potable reuse and expects to finalize the rule by 2023.

5. Is water recycling a political issue?

Congressional Democrats see it as key to solving water supply challenges in the West, especially in California and Arizona. Rep. Grace Napolitano (D-Calif.) has introduced two water recycling bills: The Water Recycling Investment and Improvement Act (H.R. 1015) would offer grants to water agencies for new projects; the Large-Scale Water Recycling Project Investment Act (H.R. 4099) would fund major water recycling projects. Neither measure has Republican support.

A Republican-supported bill, the Wastewater Infrastructure Improvement Act (H.R. 3218), sponsored by Rep. David Rouzer (R-N.C.), would help to fund water reuse projects, mainly those that recycle stormwater and wastewater indirectly. That bill lacks Democratic support.

To contact the reporter on this story: Bobby Magill at

To contact the editors responsible for this story: Rebecca Baker at; Gregory Henderson at