California is wasting water, even when we don't realize it. Our aging underground water pipelines—in some cases nearly a century old—invariably spring leaks, thousands of them that add up to 23 billion gallons a year in California alone.

23 billion gallons. That's enough water to provide for 71,000 households for a year, lost to these leaky sieves. Meanwhile water shortages from California's historic drought have led to devastated crops, left entire households with dry taps, and sparked interest in recycling toilet water.

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Yet completely overhauling the water pipe infrastructure is expensive, messy, and not happening any time soon. Instead, districts have come up with a methodical system for catching and plugging the small, hidden underground leaks. They detect these tiny breaks not by looking for them, but listening. I decided to tag along with a team of water leak detectives to see how it's done.

The acoustic loggers

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A magnetic pole is used to pry off the lid to access a gate valve below. The acoustic logger, attached to a yellow cross to make it easy to spot, is dropped into the hole.

Here where I live in Berkeley, we get our water from the East Bay Municipal Utility District, or EBMUD (eee-bee-mud), an acronym I found considerably more charming before I watched a man squat in a muddy 4X6 hole to fix a leaky pipe.

Yes, it's messy, as gushing liquid always is (it was clean water in this case, thank god), but the whole process of locating and fixing a leak under four feet of asphalt and dirt is highly methodical. It has to be. EBMUD maintains 4200 miles of pipes and fixes 850 leaks a year. The district loses about nine percent of its water a year, some six billion gallons, which is average for a water district of its size and age. On any given day, EBMUD has 75 people working on detecting and patching leaks.

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I began my morning with EBMUD's leak detection crew in the Berkeley Hills, where the roads are steep and poorly maintained. In this neighborhood where the average home sells for a million dollars, you'll still find leaning fences and cave-in sections of road—all thanks to geology. Underground streams snake under the concrete and asphalt, slowly reshaping the soft dirt underneath. Oh, and the Hayward Fault runs along the edge of the Hills. All this ground movement wreaks havoc on the water pipes below.

EBMUD has identified the Berkeley Hills are an area especially prone to water leaks, so workers are installing a network of "acoustic loggers" to proactively listen for leaks. The devices themselves resemble the metal kilogram masses you might remember from science class. They monitor the water network and listen for noise that could indicate a leak—these little gadgets are considerably more sensitive than the human ear.

In the dead of the night, usually between 2 AM and 5 AM when most people aren't awake to use water, the logger "listens." Specifically, it listens for the characteristic hiss of water escaping from a pipe. Every two weeks, a truck with a receiver drives through to pick up the radio signal from the loggers, getting a message that says either "logger found," "leak found," or "possible leak found." The latter two are grounds for more investigation.

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No digging is required to install the noise loggers. The street is actually studded with small metal covers, maybe eight inches in diameter, labeled EBMUD. Once opened, they give direct access to water pipes and valves. An acoustic logger is dropped in on top. Its presence is logged and mapped. The cover goes back on. All told, EBMUD has deployed 300 of these noise loggers to stem leakage, and they hope to eventually get that number up to 1200.

Sounding a leak

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Once a leak is suspected, it still has to be found, and EBMUD's crew uses more sounding equipment to pinpoint the leak within inches, despite being buried deep under the pavement.

A suspected leak can reach EBMUD a number of ways: the acoustic loggers installed in leak-prone areas or simply a sharp-eyed homeowner who spots a suspicious damp patch on the curb. (The one upshot to our dry weather is that it's harder for water leaks to hide.) On a quiet residential street on the southern edge of Berkeley, I met up with another crew investigating a damp spot.

Robert Aguallo, the foreman, greeted me in a hard hat streaked with dried mud. Then he handed me ear plugs and eye goggles as his crew began drilling into the ground. He had already tested the damp path for chloramine, a chemical used to sterilize drinking water at the treatment plant, to rule out a natural source for the water. Now his crew of four men were drilling four small holes, about four feet apart, in a line on top of the location of the water pipe. Water began gurgling out of two of the holes. This was an encouraging sign that they'd isolated the leak, but not a definitive one.

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Fortunately, this is a quiet residential street. Work near a major road, where the rumbling of cars will interfere with the device, would have to happen late at night when the streets are quiet.

A leak noise correlator. The single peak in the graph indicates the presence of a water leak.

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To locate the leak with more certainty requires more high-tech equipment. This is where Michael Brown and Tony Lopez came in with what's called a leak noise correlator. It works by inserting metal poles into each of the holes sitting on top of a water pipe, and attaching sounding equipment to the poles at the ends. The device sends sounds of different wavelengths down the pipe and listens at both ends. An anomaly indicates a leak.

Specific parameters—a pipe with a diameter of 4 inches, metal poles 15 feet apart—are plugged in the machine. A clear peak showing up on the screen, indicates a probable leak. The sounding poles are moved into holes closer together, until the leak is isolated. A spray-painted X marks the spot.

When Aguallo's team later digs, the X Brown and Lopez marked is off by a mere 5 inches.

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"It means the world to us," says Aguallo about the leak noise correlator. "It takes the guessing out of the whole process." At the same time, the whole system is precarious. The sounding machine is over 20 years old, so old that parts to repair it are hard to come by. (Lopez says the newer machines they've gotten just haven't worked as well.) There's only one guy who repairs it for them.

The aging leak detector reflects a larger issue with water pipes: Many of the older pipes are reaching the end of their lifespan, but budget constraints mean only 10 miles of pipe are replaced each year. EBMUD says they hope to get that number up to 40 miles a year, but even that's still a 100-year-old replacement cycle. The pipes will be in the ground far longer than they were designed to last. For now, we can only fix our broken pipes on leak at a time.

Plugging the leak

And for now, Aguallo's team will have to dig by hand. There aren't enough excavators to go around at EBMUD, so shovels it is. There's also a gas line less than a foot away from the water pipe, making excavating by machine dangerous anyway.

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After the asphalt is broken up, it's old-fashioned digging, a 4x6 rectangular hole just big enough for one man to maneuver inside. This particular leak turns out to be a relatively small one, three gallons a minute or just a little stronger than your kitchen faucet. That may not sound like much, but it adds up to over 4000 gallons a day. Minor leaks are usually repaired within a week.

Once the dirt around the pipe is dug out, the team has to work quickly. Like a weakened aorta, the now naked leaky pipe is prone to burst under water pressure. "It happens more often than I'd like," says Aguallo. The leak is a small split along the pipe's length, and the quickest fix is a stainless steel clamp that locks around the pipe. Six bolts lock it in place.

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The clamp that will be put around the leaky section of pipe.

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The clamp being installed.

Then the dirt is thrown back in and temporary asphalt poured over. (A paving team comes out a few days later.) The whole fixing process takes a few hours. This only the first of that day—Aguallo's team has two more. Over the course of a year, EBMUD fixes 850 leaks a year.

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Cleaning up around the hole before all the dirt is packed back in.

When we had first arrived at the leaky pipe site, the orange road work signs sparked an involuntary and familiar twinge of annoyance. This is how we're conditioned to deal with road work, as a nuisance that backs up traffic and dear god why does it have to be on a day you're already running late. It feels random and disruptive.

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But there's another way to think about it. Infrastructure maintenance is actually about making our lives smoother. Road work feels disruptive, but it's really about trading a major disruption—like when a water main break in LA this July spewed out 20 million gallons—for a minor one that lasts a few hours. And conserving water by fixing leaks guards against a worst case scenario that creeps closer in this drought: running out of water.

Seeing how a leak is detected from start to finish gave me an appreciation for the greater system, a symphony of moving parts that bring clean water right to my kitchen sink. There's a method behind the whole madness of water getting turned off and pipes being dug up.

Top image: Listening for tiny leaks can prevent major water breaks like this one.. Via EBMUD

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