Concrete Progress is an ongoing series of columns by Peter Brewitt devoted to exploring America’s infrastructure. It is part of Orion’s Reimagining Infrastructure project.

You’ve known this since the fourth grade: only 1 percent of the world’s water is fresh and readily accessible. Obviously there’s a little fluctuation—glaciers melt, rivers flow to the sea, shockingly expensive desalination plants get built in Saudi Arabia—but really, the water we have is all we have. While generations of fourth-graders have learned about how limited our water is, only now are grownups coming around to the need to use it carefully, efficiently, wisely. People in dry regions and in cities (and indeed in dry cities) are taking hard looks at how much water they use, limiting themselves to five-minute showers, using cooking water on their gardens, even installing greywater systems.

But over a quarter of household water use comes from flushing the toilet. There’s a limited amount you can do about that – maybe put a brick in the tank, or Let It Mellow—but in the end, when you gotta go you gotta go, and eventually you gotta flush. The flush water—“black water,” in the public works parlance—flows to the sewer, on to the treatment plant, and then, typically, out to the river or the ocean. A lot of people squeamishly don’t want to drink this stuff, even after treatment. In Orange County, California, though, they’ve gotten over themselves. The OC (as it is sometimes called), one of the most conservative, least crunchy places in the state, home to Pastor Rick Warren and President Richard Nixon, has installed a toilet-to-tap water system.

It’s important to remember that water cycles through the planet and that all the water we use today has taken many forms and flowed through many places during its eternal life. The water in my bottle today may have washed Shakespeare’s chamber pot in 1611 and dripped off Moses’s back as he ascended Mt. Sinai and satisfied a Triceratops 70 million years ago. Now, in Orange County, the process is simply sped up. Your toilet water—after it’s been purified—ends up back in your glass. Sensible enough, but to make this happen, the Orange County Water District had to pull off two tricks—boosting the rate of purification, and educating their citizens on how safe and clean treated black water actually is.

The Santa Clara Valley Water District is pursuing a toilet-to-tap water system, too.

The term “toilet-to-tap” is accurate enough, but the path from the one to the other is complex and exacting. It begins, of course, with dirty water, flowing down the pipe to the treatment facility. This water is run through layers of microfiber, which filter out solid bits. The fiber is like cheesecloth, except with much, much smaller pores—they are tiny enough to catch bacteria, and invisible to the naked eye. Then this cleaner water undergoes reverse osmosis, where the water is forced through a membrane under such pressure that dissolved substances are removed (salt can be removed from seawater using the same process). After this, hydrogen peroxide is added—the same stuff you use to clean scrapes. Hydrogen peroxide (H2O2) is essentially water with an extra oxygen molecule, which is useful for destroying contaminants through oxidation just as rust destroys iron. The water is also exposed to ultraviolet light: UV radiation kills disease-spreading microorganisms.

At the end of all this, the water is comparable to distilled water, and purer than the groundwater that makes up the bulk of OCWD’s supply. The purified water, 70 million gallons per day, is sent to recharge basins to keep OCWD’s aquifer full. You can drink it directly, though—at the district’s plant in Fountain Valley, visitors are offered a glass. Reclaimed sewer water provides about a fifth of the district’s water. If OCWD didn’t do this, it would have to import water from elsewhere, which would be 30 percent more expensive, not to mention an added pressure on the environment at the point of those waters’ origin.

I’ve said it before in this space: it was a really dry summer in California, and it’s been dry for years—this is undoubtedly part of why they’re willing to try new things. Orange County’s toilet-to-tap program began in 2008. Such programs have been considered in a lot of places, but until recently, public disgust has been too much to overcome. The OCWD preempted this by reaching out to the community: according to Southern California Public Radio, the OCWD presented the facts more than 2,000 times, to be sure that people knew just how filtered their water was going to be. This has allowed not just for success, but expansion. By the end of next year, OCWD will have expanded to 100 million gallons per day, saving money and water and leading the county into the future. (I enjoy imagining the expensively dressed high schoolers of the OC drinking black water.) Toilet-to-tap is happening elsewhere, too, from El Paso to Virginia.

On a personal note, this’ll be my last column from California. I’ve moved from Santa Cruz to Spartanburg, South Carolina, where I’m a professor of Environmental Studies at Wofford College. To readers from the South: in the comments, please do let me know about any exciting reimagined infrastructure projects out here. I’ve already learned about a few—the movement is nationwide.

Peter Brewitt has wondered about infrastructure ever since a flood kept him away from three days of kindergarten. He is a professor of environmental studies at Wofford College. He wrote his doctoral dissertation on dam removal politics at the University of California, Santa Cruz, and is devoted to understanding how people decide to restore and remake their environments.