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Street-closing water main breaks may send hundreds of gallons per minute into a utility’s water losses, but they’re not the biggest water wasters for most organizations, according to engineers at Flow Metrix, Inc., an 11-year-old manufacturer of leak-detection solutions. According to the Flow Metrix team, the very visible torrents from burst mains typically account for less than 1% of a utility’s water production.
On the other hand, a service line leak of 6.5 gpm will lose more water than a main break every 90 days and will typically run unde-tected for several years.
That means utilities might want to plug the unseen leaks when trying to cut unaccounted-for water. Research conducted by American Water is now proving that utilities can detect, find and stop water leaks long before big problems bubble up in the streets. What’s more, fixed network or mobile automatic meter reading (AMR) networks can play a role in speeding information to engineers for quick repairs.
As the largest water services provider in North America, American Water fills faucets for more than 18 million people in 29 states and three Canadian provinces. The company, which is headquartered in Voorhees, N.J., chose its Connellsville, Pa., location to test a new leak detection program for several reasons.
First, Connellsville purchases all the water for its 4,700 service hook-ups from other utilities.
"It's costing us more for the water than if we had our own filtration plants and produced the water ourselves," said Tom Barozzini, supervisor of network operations and non-revenue water for the utility.
Along with paying extra, Connellsville is losing a lot of water to aging infrastructure and hilly geography, Barozzini explained. Some of the town's water distribution system dates back to the late 1800s, and much of it runs via 2-in. mains made of galvanized steel. In addition, the town sits atop a hill overlooking a river. When leaks occur, they can easily run downhill, undetected.
Barozzini said that Connellsville’s non-revenue water reached as much as 29%, and he likens these unaccounted-for gallons to lost inventory.
"If you're making cars and 29% of the vehicles coming off your assembly line aren't getting bought, you're losing money," he said.
Old problem, new technology
To combat losses, American Water teamed with Hexagram, Inc. for a fixed-network AMR solution and Flow Metrix for MLOG leak-detection sensors that can piggyback data onto the AMR system's communication stream. MLOGs are stand-alone, battery-powered units that contain both a sensor and small computer, said Paul Lander, president of Flow Metrix. He explained that when a leak is present, it sets up a pressure wave inside water pipes, and the sensors pick up the vibrations hundreds of feet away.
When attached to water pipes near a service meter, the sensors wake up and record vibrations for a four-hour period of time in the quietest part of the night. The units hear leak vibrations in the area, but have no way of determining precisely where those leaks are. For that, Connellsville managers dispatch crews armed with more traditional leak localization and correlation equipment.
Although Connellsville has 4,700 meters in service, the utility has, so far, placed only 487 sensors and AMR units throughout the community. This leaves the meter/sensor combinations spaced about 500 ft apart and placed on one out of every 10 service hook-ups.
"We have a few holes where installers couldn't get into homes," Barozzini said, "but we're pretty well covered as far as listening for leaks." He estimated that his current sensors and AMR units catch leaks for around 80% of his distribution system, and he has more units on order to fill in the gaps.
The sound of money
As soon as installers finished putting units in place in April 2005, Connellsville engineers started spotting possible leaks and plugging up water loss. The utility's leak detection successes really picked up after a few months, Barozzini said. In part, that may be because the sensors maintain historic data in their on-board computers, compare each night’s acoustic input to what has been heard before, and get better at screening out ambient noises such as restaurant ice machines, household clatter or even the hum from a loud voltage transformer atop a nearby power pole.
So far, Connellsville's leak-detection team has found at least 25 leaks through the sensors.
“Those leaks would have never been discovered before because of where they were located,” Barozzini said.
Barozzini also reported that the utility is saving approximately 350,000 gal a day. The system delivery numbers-the amount of water purchased and put into the system each day-are lower than he’s seen in his 16 years on the job.
Barozzini noted that while customer meters are read monthly, the utility's billing follows a somewhat irregular schedule of two four-week periods followed by one five-week period. For that reason, there are times when not all accounts make it into the billing cycle, and unaccounted-for water looks quite high. The next month, when more meter reads appear in the bills, unaccounted-for water plummets.
"I looked at last month's unaccounted-for water and it was 3.8%," Barozzini said. However, he said he knows the numbers won't be nearly as high the following month, when more bills go out. In addition, there are monthly variations to consider. "We had a 10-in. main blow out the other night. That will have tremendous impact on the numbers" for non-revenue water, Barozzini said.
According to Lander, his organization used engineering software and Connellsville’s actual production data to calculate how much non-revenue water has dropped.
"Our estimate is that Connellsville's production has been reduced somewhere between 15 and 25%," Lander said.
He added that some of the savings comes from reduction in blow-offs. Utilities use system blow-offs to vent water and thereby avoid stagnation or water quality problems. When the sensors heard this activity, engineers decided they could turn the blow-off volume down a bit. According to Lander, that shaved almost 5% off the non-revenue water figures and saved American Water between $10,000 and $15,000 annually.
In Connellsville, sensor data comes in nightly along with AMR readings from the utility's Hexagram units. American Water also has related leak-detection programs underway in Uniontown, Pa., and Manville, N.J., where only sensors are in place.
"A leak starts small," Lander explained, adding that it takes up to two years before a leak creates a major problem like a burst pipe. And, he said, the sensors catch leaks when they're still tiny, so a delay of a month or two before collecting sensor data and fixing the leak won't waste very much water.
In fact, the sensors are sophisticated enough to guess the age and size of a leak based on the sounds those leaks make. New, small leaks produce a fizzing sound as water comes out of a tiny hole or crack very quickly and under pressure, Lander said.
"That generates a sound with certain frequency characteristics," he added, noting that water coming out of larger, smoother holes generates a different sound altogether. This enables the computers in the sensors to make some intelligent guesses about the size of the leak, allowing utility managers to prioritize repair efforts.
Either way—with fixed-network AMR units or without them—American Water is plugging leaks and cutting losses.
Reducing non-revenue water isn’t the only benefit this partial AMR deployment has brought to Connellsville.
"The fact that 500 of our meters can now be read by pushing a button on a computer" is a "huge savings labor-wise," Barozzini said.