Finding Leaks at the Source
Leak detection plays a vital role in water conservation, allowing lines to be repaired before
a catastrophic failure takes place.
While to other countries, the United States is considered relatively young, our infrastructure is aging. When it comes to our water distribution networks, utilities and municipalities can benefit from detecting smaller leaks before they surface or become catastrophic.
Not only have small leaks been shown to be precursors to larger leaks and failures, repair of an existing leak means bringing non-revenue water back into the system. Leak detection not only plays a vital role in water conservation, but in the framework of risk management, allowing lines to be repaired before a catastrophic failure takes place requiring street and business closures, overtime pay for workers, and inconvenient shutoffs for rate payers.
Tried and True
Traditional methods of finding leaks remain relatively unchanged, listing for them. Listening for, and then tracing, a whoosh, clink, or hiss back to its source is done in assorted ways with various types of equipment.
Operators can walk the length of pipe, listening to the ground with microphones and headsets. This method is time-consuming and often only used when trying to pinpoint a leak detected by other means.
Data loggers are frequently used to collect measured noises within a pipe. They can be left in place for a set amount of time, say 30 minutes or longer, based on the type of information being gathered. Collection of data from the loggers can be performed, either by removing the logger and downloading the data or via radio to personnel walking or in vehicles.
The primary purpose of the Miami-Dade County leak detection program is saving water, which is a scarcity in South Florida.
Miami-Dade uses three types of loggers placed 500 feet apart and programmed to collect five-minute readings over the course of an hour.
At the end of the day, loggers are returned to the data management unit, where data is downloaded and analyzed.
Using two sensors, a correlating logger measures the time it takes for the sound to reach each of the sensors and uses this to pinpoint a location of a leak. Smaller leaks make less noise, so the trick is to find small leaks before they cause major failures. But that’s easier said than done.
“We find leaks as small as two gallons a minute,” says Griff Machinski, account manager Fluid Conservation Systems (FCS), manufacturer and distributor of various types of leak detection equipment. “But there are variables like how close the leak is to one of our sensors. The smaller the leak, the closer it needs to be to the sensor.”
Miami-Dade County provides potable water under the watchful eye of the South Florida Water Management District (SFWMD) and uses three types of loggers to look for leaks in their system. The primary purpose of their leak detection program is saving water, a scarcity in South Florida and a requirement by the water management district.
“With our annual pumping permit, we’re required to have a leak detection program in place,” explains David Bridges, assistant superintendent for the water transmission and distribution division of the county’s water and sewer department, the largest public utility in southeastern US. “Initially in the 1980s, we had 30 to 32 people with traditional leak detection equipment, aqua scopes, and geophones walking the entire system, each foot of pipe. In the 1990s and 2000, we began purchasing the loggers and correlating loggers, and it advanced us greatly. Now we have 14 people in the field and we cover the entire system, water mains, and service lines, at least once every year.”
Deployment units pick up equipment from the data management unit at the start of the workday and review the water distribution atlas and develop a deployment plan. Deployment crews conduct field surveys and locate leaks using three types of loggers: the Aqualog-80 (FCS), SoundSens Logger (FCS), and Zcorr Digital Correlating loggers (Itron). All loggers are placed 500 feet apart and programmed to collect three five-minute readings over the course of an hour.
“They say you can cover 1,000 feet, but when we shorten it to 500 feet we get better results,” says Bridges. “But it depends on the type of pipe too. We deploy at 250 feet, and with PVC and pipes that are larger than four inches in diameter. Most of our pipes are less than 16 inches in diameters, so this approach works well.”
The crews also use aqua scopes on 24-inch, 36-inch, and 42-inch diameter pipes, because the access points on larger pipes are further apart.
“We’ll walk in between points with the traditional equipment,” says Bridges. “And we’ll put it down every 10 to 15 feet.”
At the end of the day, loggers are returned to the data management unit, where data from the inspections is downloaded and analyzed. If there appears to be a leak, further inspection is ordered.
Pinpoint units, as their name implies, pinpoint the exact location of the leak using geophones and aqua scopes. The county has found this equipment works better than correlators, because readings can be affected by pipe conditions, such as build up or a change in pipe size between correlation points.
When data is reviewed and leaks confirmed, the data management unit creates a work order ticket. The time from finding a leak to repairing the pipe is usually two weeks.
“When we first started the program in 2000, we found about 2,000 leaks; now we find about 1,400 leaks a year,” says Bridges. “Of the leaks we find, 80 to 90% have not broken ground and 10 to 20% have. When we started, it was the complete opposite. We’re more proactive and catch leaks before they get too big. It reduces the cost and the amount of water loss.”
Overall, Bridges is pleased with the program. So much so, that they have trained other utilities from as far away as Colombia, South America, and, most recently, a group from Albuquerque, NM. Bridges wants other utilities to be able to learn from their experience. “We don’t push any one product—we just explain what we have and what works,” he says. “I’ve learned that you have to be able to look at the market. What works well in one area may not work well in another area.”
The City of Chicago, IL, has found success in reducing water use, but not just from the leak detection program. The city is systematically replacing older pipes in the network, some of which date back to the 1890s.
“The increased water main replacement program has been a benefit and is likely the biggest contributor to our reduction in water usage,” says Mike Sturtevant, with the City of Chicago Water Department. “In 1990, our usage was 780 mgd [million gallons a day]; now it’s 512 mgd. Leak detection, as well as other conservation measures, have also contributed significantly.”
The city’s system includes 4,300 miles of pipe. Leak detection is performed only on smaller pipes, 16-inches in diameter or less. Chicago performs the majority of its leak detection by contract. They have been using ADS LLC, a company that provides both equipment and services such as leak detection for the City and hydraulic valve operation.
Sahara is an acoustic probe tethered to a cable drum.
In Chicago, 1,200 to 1,500 miles of pipe are inspected for leaks every year, covering the entire network every four or five years. There are areas that are inspected more frequently, like The Loop, where a catastrophic failure would be a costly disruption.
“There is definitely a monetary savings to leak detection,” adds Sturtevant. “When you have a leak, you’re losing water.” And when you lose water, you lose money.
Divide and Conquer
While ADS does perform continuous leak detection services, they also suggest narrowing down the areas mostly likely to have water that’s unaccounted for.
Luis Mijares, manager of water services and water products for ADS LLC, recommends what they refer to as District Measurements, where water going into an area is measured and compared to the volume of water being used. The difference in measurements is non-revenue water. District sizes vary and are often determined by criteria such as topography and the number of valves or pressure zones.
“We temporarily close the valves off, so there are only one or two entrances and one or two exits,” says Mijares. “The flow measurements indicate where leaks are likely. It’s expensive to listen to hundreds of miles of pipe. It’s more cost effective to narrow down an area to listen to by performing District Measurements.”
Mijares recommends that clients start with District Measurements and evaluate an area over a period of 24 to 48 hours. Measurements are collected every 15 minutes to record the diurnal pattern of water demand. Unless a district has an unusual nightly water demand, such as facilities with large night shifts or irrigation demands, water use should be at a minimum around three or four in the morning. Flows are then compared to total volume in the district and the percentage lost is calculated. The percentages are used to rank districts in order as to where leak detection will be used, allowing utilities to manage workflow more effectively.
ADS field crews utilize correlators with accelerometers and hydrophones and correlating loggers to listen to leaks and determine their location. From there, the surface is painted and a repair ordered. Mijares stresses the importance of knowing the pipe diameter and material, along with the actual path of the pipe.
“Noise travels through the pipe at different velocities. Noise in plastic pipes is much slower and attenuated than metallic pipe,” says Mijares. “Even correlators can give an erroneous reading if the input data isn’t correct, or in a situation where a ductile iron pipe was repaired with a PVC patch. We correlate down, then listen with a ground microphone, and then listen again.”
The Birmingham (AL) Water Works and Sewer Board (BWWSB) also uses district metered areas (DMAs). The board performs all the work in-house. When the board gets a SCADA (supervisory control and data acquisition) reading showing a potential leak greater than 10%, patrols are sent out to collect data from the Permalogs in installed in the area.
“It keeps people off the streets, because 95% to 98% of the time there’s no leak; they’re listening to nothing,” says Geoff Goodwin, manager of revenue water. “This gives us more time to be productive, not listening to pipe that’s not leaking.”
Large Pipe Dilemmas
Bill DiTullio is the president of InfraMetrix LLC, a company that provides leak detection services ranging from fieldwork, collecting data, identifying leaks, and performing maintenance. As part of the inspection process, DiTullio has seen the difficulties in identifying leaks in larger pipes and knows the benefit of using an in-line acoustic device, such as Sahara (by Pressure Pipe Inspection Company) or SmartBall (by Pure Technologies Ltd).
“With in-line acoustics, you’re never more than one pipe diameter away from the leak,” says DiTullio.
In DiTullio’s case, using Sahara or SmartBall usually comes after other assessments have been performed, including a tabletop analysis of pipe and system information and possibly a condition assessment. Based on this information, DiTullio may recommend in-line acoustics.
Brian Mergelas, president of Pressure Pipe Inspection Company (PPIC), admits that initial interest in Sahara has come from private water companies where water leaks impact profits and managers are held accountable to lost revenue.
A parachute on the probe allows it to move with the water, and the cable allows the operator to control the movement, pulling the probe back over a suspect sound like a fishing reel pulling in a fish.
Using an in-line acoustic device helps to identify leaks in larger pipes.
Sahara is an acoustic probe tethered to a cable drum. A parachute on the probe allows it to move with the water, and the cable allows the operator to control the movement, pulling the probe back over a suspect sound like a fishing reel pulling in a fish.
A GPS system is used during the inspection to locate the leak in a database. The surface is marked with paint. The probe also serves as a base to mount a camera or other technology to measure pipe thickness.
As part of a five-year strategic plan for water conservation, The Dallas (TX) Water Utilities ramped up their leak detection program and began using Sahara.
“In 2004, in the beginning of the program, we quickly noticed that we weren’t finding any leaks in the large diameter pipes,” says Randy Payton, senior program manager of the utility’s distribution division. “We did a study and brought in Sahara, and they found leaks.”
The utility now uses Sahara technology to monitor a majority of pipelines 16 inches or greater in diameter. The utility still uses more traditional methods of leak detection (Permalog MK3 and AccuCorr 3000) for its smaller diameter pipe. In the small diameter pipes, they have identified 1,060 unknown leaks (an average of 0.21 leaks per mile), and in the larger pipes they’ve found 73 leaks (an average of 1.5 leaks per mile).
Initially, the Dallas utility was staffed with four members, with a plan to survey the network every 10 years. Because of the success of the program, the city council has approved funds allowing the program to expand. The staff is now up to 14, and the frequency of inspections has increased, so a full pipeline inspection will be completed every 2.5 years.
Even though failures cannot be completely predicted, Payton can see the benefits of identifying unknown leaks in the system, whether they are from large or small pipes.
“There are reduced water loss and a cost savings for water treatment,” says Payton. “There are decreased disruptions to customers. Not to mention a reduction in liability claims from damage caused by unknown leaks.”
SmartBall, is another tool to help utilities identify smaller leaks in larger pipes before they become catastrophic.
“The SmartBall is a free swimming tool that identifies leaks in larger pipes,” says Mark Holley, president of Pure Technologies, US. “Pipe diameters 10 inches or larger are its sweet spot. The unit has a battery life of 15 hours and can travel through tens of miles of pipe, as long as there’s enough velocity. It’s extracted at a downstream location.”
As it travels, the ball is listening and recording noise from the pipe. The ball is made up of an aluminum core with holding electronic equipment. It’s covered with foam, similar to a Nerf ball.
“Typically, the ball sinks to the bottom of a pipe. It uses SmartBall Receivers and contains an accelerometer that tracks velocity to pinpoint a leak. There’s a lot of technology in a little ball,” says Holley.
The sensors help track the distance the ball has traveled, but this is backed up with other data. Sensors are mounted on a flange. The ball chirps as it rolls through the pipe, and the chirping is picked up by the sensors.
The ball is extracted by pushing a rode into a 4-inch full port valve. A net expands from the rod and captures the ball. But before it’s extracted from the pipe, simulated leaks are performed. A small half-inch spigot valve is used to create a leak at certain flow rates. This information is recorded by the SmartBall and compared to information collected during it travel through the pipe. Using this data, an estimate on the volume of the leak is provided.
After the ball is extracted, the data is downloaded from its memory.
“The technicians usually go back to their hotel rooms to evaluate the data while they are still in the area of the job site,” says Holley. “If leaks are identified, they are marked on the surface the next day. They also produce a PDF report of data related to the inspection, the type of pipe, diameter, and number of leaks. It’s integrated with Google Maps; in case the utility doesn’t address it right away, they still know the location.”
In Birmingham, BWWSB recently completed a pilot study using the SmartBall. One mile of transmission main was tested, and three separate leaks were found. The BWWSB plans to use SmartBall in 200 miles of its transmission main.
“We were limited because the transmission main is concrete so it doesn’t transmit sound very well, and it doesn’t have access ports,” says Goodwin. “You want to find leaks when they’re small—before they wash away part of an interstate.”
For areas with an unusually high probability of failure, it may not be cost-effective to frequently send crews out to monitor for leaks. In this situation, remote monitoring may be more feasible. Remote monitoring utilizes radio signals to relay leak sound data to a handheld unit in the utility’s moving car.
This is the case on the Island of Oahu, HI, where heavy rains cause the ground to shift. The island has seven “slide areas.” Rather than sending crews out after every heavy rain event, 300 Sewerin SePem loggers were purchased and installed in the slide areas. The program is still considered to be in the testing phase, but so far leak investigators have been able to drive by with a reading device that collects data transmitted by radio signals from the loggers. Now crews can cover a slide area in half a day, compared to a week or two prior to the installation of the system.
These proactive measures taken on by the Honolulu Board of Water Supply (HBWS), HI, supports Honolulu Mayor Mufi Hannemann’s drive toward sustainability. The Mayor’s Vision for the 21st Century Ahupua‘a (Ahupua‘a is a term for a swathe of land from the top of a mountain or volcano down to the shore) called for a 10-year plan with several goals, one of which benchmarks water conservation.
As an engineer with the HBWS, Carolyn “Cat” Sawai is coordinating the Internal Water Conservation Program geared to reduce water loss in the pipeline system.
“The leak detection program is part of an internal conservation program that focuses on utility controlled conservation and includes proactive repair,” says Sawai. “We still have to repair the pipe, but we find it before it’s catastrophic. This should result in less overtime. We can notify customers, and the repair can be planned accordingly. It saves money and natural resources and improves customer service.”
The slide areas are predominantly in residential neighborhoods, with smaller pipes ranging in diameter from 4 to 12 inches. When it came to choosing the right product to monitor the slide areas, Sawai and her team put a lot of work into the request for proposals (RFPs).
Initially, Sawai’s department purchased a small trial set of loggers and operated them for almost a year to learn as much as they could. Issues like screen size on the handheld unit became apparent as did battery life and spacing between loggers. After that, they were ready to prepare the RFP and start the selection process.
“We wanted to be fair to the vendors and make sure that we got what we needed,” says Sawai. “The issues that were most important to us were the integrity of the system, speed and distance criteria for drive-by pickup of the information, and a failure rate of less than 10%, meaning when we drove by, we needed to pick up signals 90% of the time, and it had to find the leak. And then there were the intangible things. We wanted to know about their customer support, so we called their clients. We wanted to make sure the company was sound and reduce the potential to contract with a company that went out of business or will be absorbed. All of these issues actually ranked higher than cost, which was only 20% of the decision process.”
Integrity was determined as part of a four-day test. A set area was defined, and vendors were invited to find small leaks on the laterals. Vendors were limited on the number of loggers they could use to verify their spacing specifications.
“We thought about what the most essential information was that we needed,” says Sawai. “You have to think about it like it’s your own money. We even wrote in the RFP the required battery life. We expect a seven-year life, and if it doesn’t last that long, we get a replacement under warranty. If the equipment becomes obsolete, they’re required to keep parts stocked for 10 years or provide no cost upgrades.”
The BWWSB in Birmingham also utilizes FCS Permalogs on about 1,000 miles of its water line.
“We do a manual patrol,” says Goodwin. “We drive by, and if we keep the speed down to about 30 miles per hour, it’ll read. It’s been a real benefit—what used to take 14 months, our crews can do in 6 weeks.”
Sensus has also paired products with FCS to provide wireless data collection. The Sensus FlexNet can be used with FCS’ Permalog+ AMR to allow utilities to collect data day or at night when activity is at its lowest.
“This makes it easier to hear smaller leaks,” says Tom Galuska, product marketing manager for AMI water with Sensus. “Without sending them out at two a.m., our goal is to catch it before it becomes a big leak,” keeping crews safe while saving water and money.
Author's Bio: Diane McDilda is an environmental writer and author living in Gainesville, FL.