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Environment & Science

Purple pipe means recycled water. Why purple?

Purple pipes, Stanford University, Palo Alto, California.
Purple pipes, Stanford University, Palo Alto, California.
John Loo/Flickr

Large property owners like cemeteries and golf clubs are among the few who can use recycled water through most Southern California water systems. A special pipe, it carries sewage water that’s been filtered for solids and cleaned of some impurities.

This sort-of cleaned-up water can irrigate landscaping; it can cool equipment in industrial uses; it can be what you flush, say, in an office building or a hotel. As some of its advocates point out, it's the same water dinosaurs drank.

And it all happens through a pipeline that’s a distinctive color halfway between a field of lavender and Violet Beauregard after she licked the blueberry wallpaper (or Gene Wilder's waistcoat, whichever Willy Wonka reference you like). 

One pioneer of recycled water here in Southern California is the Irvine Ranch Water District.

The district dates back to 1961. From near the beginning, the IRWD Board of Directors decided to place a premium on recycling water. By 1967, Irvine delivered 2 million gallons a day of tertiary-treated water to agricultural users. The district was the first in the state to get a permit to use recycled water for any acceptable use (not just agriculture; that includes industrial and irrigation uses, and some plumbing). 

Irvine Ranch put two parallel delivery systems next to each other, a system  called dual distribution. It was cutting edge nationally back in 1985, when the EPA featured it among a few places, including Colorado Springs and St. Petersburg, that had incorporated recycled water in their urban plans. 

Irvine Ranch is the district that picked the color for recycled-water pipe.

“There are pipe color designations that tell those handling the systems what they’re dealing with,” IRWD’s Mark Tettmer told me. “When recycled water came along, the industry decided it needed a color to help differentiate it from the other things that are already on the property.”

In cities around the United States, blue is for potable water. Green is for sewers. Yellow signifies natural gas, oil, petroleum, or something else that’s potentially flammable. Orange is for telecommunications. Red is for power lines. And white is for marking where excavations and new pipe routes will go.

So that’s one reason why purple. “Because it’s a color that wasn’t already spoken for,” Tettmer says, referring to American Public Works Association standards. “Wherever recycled water is used, purple pipe is used, which is known as ‘Irvine Purple,’” the IRWD website proudly touts

But the story also involves an engineer named Keith Lewinger. The story goes that Lewinger picked out the lavender-painted pipe because he could distinguish it even though he’s severely color blind. If he could identify it, went the reasoning, so could others.

Lewinger moved on from Irvine a long time ago. He retired as General Manager from the Fallbrook Public Utilities District in San Diego three years ago, and when he did, Congressman Darrell Issa thanked him for his service on the House floor. 

Still, Irvine holds on to purple pipe’s origin story – mostly as a teachable tool. IRWD’s Mark Tettmer says an unexpected boon of purple pipe is that people remember it, which helps with public education.

“It’s a pretty conspicuous thing,” he says.