The idea of drinking water that was recently sewage swirling down your toilet bowl, shower drain, or kitchen sink may sound pretty icky. But experts say it's actually nothing to be squeamish about — and it might be coming to your state and city soon.

It's a water recycling method known as direct potable reuse, or DPR, which sends highly treated sewage water almost directly to a drinking water system for distribution to communities. It's legal in Texas, and legal on a case-by-case basis in Arizona. Multiple other states are in the process of formulating regulations to legalize it too, including California, Colorado, and Florida.

The water produced by DPR meets federal drinking water quality standards, experts say. And there's a growing movement to urge people to warm up to the idea of DPR and other sewage recycling methods, which were once dismissively labeled "toilet-to-tap."

"People need that change in mindset, forgetting where your water came from and focusing more on how clean it is when it's in front of you," Dan McCurry, a civil and environmental engineering professor at the University of Southern California, tells CNBC Make It.

Recycling wastewater can help avoid drinking water shortages

The process might not sound appetizing, but DPR can prove invaluable when drinkable water becomes scarce.

Climate change alters patterns in rain and snowmelt, which sends less fresh water to crucial, natural drinking water sources like the Colorado River, Lake Mead and Lake Powell — all of which face severe water shortages amid extreme drought conditions. Growing populations that demand more drinking water will only stretch those sources thinner, making methods like DPR all the more essential.

Two cities in Texas — Big Spring and Wichita Falls —  have used DPR to bolster drinking water supply so far. El Paso is planning to follow suit, alongside major cities like Los Angeles and San Diego once state DPR regulations are in place.

Wichita Falls implemented DPR for about a year, starting in July 2014, as an emergency solution to a harrowing five-year drought. Chris Horgen, the city's public information officer, says DPR produced 5 million gallons of treated water each day for the city, representing a third of the drinking water distributed to taps.

"The state was that close to delivering water bottles to us in that final year," Horgen says. "That's what would've happened without DPR."

In El Paso, DPR isn't live yet, but the project is underway with a goal of building a long-term sustainable drinking water supply. Diversifying the city's drinking water sources could better prepare it for severe droughts that threaten natural sources like river water, says Christina Montoya, communications and marketing manager at El Paso Water Utilities.

"It's a way to make sure that El Paso will thrive 50 years out from now," she says. "We can't just be planning when an emergency happens. We need to be planning all the time for the future."

Wastewater recycling is nothing new

If you're still feeling squeamish about DPR, know that it's nothing new: There might already be recycled sewage in your drinking water. Several cities in the U.S. have used a similar system called indirect potable reuse, or IPR, for decades.

In that system, sewage water is treated at a wastewater treatment plant, which cleans it to a level that meets the standards for irrigation, or for watering land and crops. The water then gets sent to an advanced purification facility, which McCurry says cleans the water even more, typically putting it through a three-step process that ensures it meets or even exceeds state and federal standards for drinking water quality.

By this point, the water is clean. Still, it then goes into an "environmental buffer" like an underground aquifer, where it can spend months or even years to undergo further filtration. Finally, it goes to a drinking water system for distribution, McCurry says.

DPR cuts out that environmental buffer step, eliminating time, cost and energy from the process, McCurry says. In some cases, the water gets sent directly to taps. In other cases, it gets mixed with raw water — like lake water, for instance — before entering distribution.

Research shows that advanced purification facilities can consistently treat sewage to safe drinking standards without that extra step of an environmental buffer, which is "really not necessary," says Patricia Sinicropi, executive director of water industry trade association WateReuse.

"That technology can really take any type of water from any source and purify it to the point where the average consumer will have a good experience drinking it," she says.

How cities are eliminating the 'yuck factor'

More than two decades ago, political rhetoric and media sensationalism sparked heavy public resistance to the concept, resulting in abandoned projects in cities like Los Angeles. A 2015 survey of 2,000 people across the U.S. found that 13% definitely refuse to try recycled sewage, 38% are uncertain and 49% are willing to try it.

That's why some cities are launching test runs first.

San Diego operated a small-scale advanced purification facility from 2009 to 2013 that successfully demonstrated that DPR can treat sewage water to safe drinking water standards. That demonstration facility didn't distribute any water to taps — making it perfectly legal — and it allowed the public to visit and try the water being produced.

In El Paso, a demonstration facility successfully ran its course for eight months in 2016, according to Montoya. Soon after, the city gained approval to develop a large-scale facility to carry out DPR, which will likely be finished in 2026 and produce about 10 million gallons of drinking water daily. Ninety-six percent of citizens said they were supportive of the city's DPR plans after visiting the demonstration facility.

"We know that the technology can treat wastewater to some of the purest water out there. But it's that challenge of public acceptance for other parts of the country," Montoya says. "People just need to understand how important it is."

Los Angeles has a similar plan to avoid repeating history. Jesus Gonzalez, manager of the recycled water program at the Los Angeles Department of Water and Power, says the city will open a demonstration facility at the heart of the city by late 2024 to serve as a "proof of concept," after California legalizes DPR and finalizes regulations by the end of 2023.

"We want to eliminate the 'yuck factor' or people's negative perception," he says.

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