Water impacting directly on the soil produces a beating or rapid thumping sound, while water flowing into the soil and around a pipe, as shown here, sounds like a babbling brook or mountain stream. Photo courtesy of Subsurface Leak Detection.

Plumbers are often the unsung heroes for business people and homeowners with unseen and yet very real problems-water line leaks.

With the proliferation of slab homes that encase water lines, sewer lines, electrical conduit and sometimes air ducts under concrete, being able to locate and detect the source of a water leak has become a large and profitable niche in the plumbing trade.

"Leaks are a big business, especially with so much new construction going on today," said Jimmy Carter, director of corporate field services for American Leak Detection in San Bernardino, Calif. "Sometimes the leaks develop because of construction defects, where there is too much hurry to lay a pipe or a pipe becomes kinked and is overlooked."

Carter noted there are plenty of ways besides construction defects that can lead to leaks in water lines.

"Sometimes a pipe is laid next to a stone. When water runs through the pipe, it may eventually wear a hole in the pipe wall next to the stone and cause a leak," he said.

Carter pointed out that he has also seen plenty of electrolysis problems develop with copper pipes.

"In some areas of the country with a high acidity in the water, problems can develop if electric lines run nearby," he said. "Sometimes you get a current working that causes electrolysis. And remember that some houses use the cold water line as a ground for electricity."

In the Palm Springs area, Carter said he has seen calcium deposits build up in a water line, break off later and make a small divot in the interior of the pipe. Electrolysis then helps wear a hole in the pipe, causing a water leak.

"Most of our problems in that area develop from the inside out in cold water lines," he said.

In contrast, Carter has seen more problems with hot water pipes in the San Diego area.

"As the water gets hot in the pipes, it can have a reaction with the soil content, which then acts on the outside of the hot water line," he said. "That's where we have problems from the outside in."

American Leak Detection celebrated its 30th year in business last year and has 300 franchises worldwide. It has manufactured its own leak detection equipment since it started business in 1975.

"We put all the filters a plumber can need into one leak finder, our XLT 50," Carter said. "And we also make LeakTell, which defines fluid loss in any type of body or water, like a swimming pool or standpipe."

Subsurface Leak Detection of San Jose makes two models of water leak detector, among other products-the LD-12 "Professional's Plus" and the LD-7 that fits in the palm of a user's hand.

Steve Carson of Subsurface said the LD-12 is very useful for slab leaks and features an amplifier with meter display and filter controls, ground microphone and hand switch, and stereo headphones.

Carson said there essentially are three different, commonly-identified sounds produced by water leaks in underground pressurized water pipes:

• pipe resonance and vibration from orifice pressure reduction;

• water impaction on the surrounding soil; and,

• water circulation and flow in the surrounding soil cavity.

Pipe vibration, or resonance, often is the loudest and most intense leak noise that a plumber will hear, sounding like a whoosh or a hiss.

Water impaction and circulation often are weaker and may only be heard when the listener is very close to the leak or directly over it, he said.

Water impacting directly on the soil produces a beating or rapid thumping sound, while water flowing into the soil and around a pipe sounds like a babbling brook or mountain stream.

According to Carson, there are a number of factors that affect the loudness and frequency of the sounds transmitted to the surface by water leaks. These include the water pressure in the pipe, the pipe material and its diameter, the soil type and compaction, the depth of the soil over the pipe, and any surface cover, such as grass, loose soil, asphalt or concrete.

Leak detection units are essentially listening devices with a sensing element and a piezo ceramic transducer that turns vibrations into a small current, Carson pointed out. The current is then amplified so the operator can hear it through earphones. But sound is often muffled, so operators often only hear low frequencies from 50 to 1,200 hertz, or perhaps between 600 and 800 hertz if the pipe is deep in the ground.

"Sound travels up and down a pipe very easily," Carson said. "When you listen directly on a pipe you can hear a leak very clearly as opposed to some other noise."

Vern McCollough has owned an American Leak Detection franchise in Tulsa for ten years and employs 13 people in his business that deals exclusively with leak detection and repair.

"I would prefer to hire people with little or no plumbing experience and train them in leak detection and plumbing skills," McCollough said. "We've found that when we hire experienced plumbers, we have to put them through a de-training process in order to develop their leak detection skills."

McCollough has two drain and sewer repair crews working all the time, and the rest of his team is out in the field performing leak detection on potable water systems, pools and spas.

While the primary job of his technicians is leak detection, they will do repairs to the lines as needed.

"We've also been moving more heavily into commercial work for the last three years," McCollough said. "But it requires a lot of different equipment, like a jetter, which is a necessity for that kind of work. And we perform leak detection work on a lot of fire suppression systems for commercial buildings, but the repairs are generally done by someone else."

McCollough noted that during the summer his crews do leak detection and repairs on about six swimming pools and spas each day.

But the primary leak detection work that his company does is for plumbing companies and homeowner's associations.

"We work for all the plumbing companies in our area, especially detecting leaks under slab homes," he said. "If a plumbing company calls us out to detect a leak, once we find it, we hand the repair job back to them. If we're called out by a homeowner's association or an insurance company, then we'll perform the repair."

McCollough said that for a typical call, one of his plumbers will arrive at a home and find the water meter turning but no water running inside the house.

"We'll either find water all over the place from the leak or no water at all," he said, noting that often his company is called into to work a job where another plumber couldn't find a leak.

"Some plumbers feel a responsibility to take on a leak detection," he said, "but often they don't have the skills or equipment to handle the job. We've honed our skills because we do so much leak detection."

McCollough estimated his technicians average between three and five leak detections per day.

"Regular plumbers don't get that kind of experience," he said.

Another American Leak Detection franchise owner, Bobby Knell of Dallas, has been solely in the leak detection and repair business since 1987. While nearly half of Knell's work revolves around leaks in water lines under slab houses, a large percentage of his business has developed in swimming pools and spas.

"On the pools, we handle gunnite pools, as well as fiberglass and in-ground vinyl liner pools," he said. "But some of the most difficult leaks to detect are those under a slab where the water pipe is sleeved in plastic. When it leaks, we can't hear it as easily as an unsleeved pipe."

Knell added that nothing helps to find a leak when a pipe has been sleeved in plastic: "Sometimes we have to make a hole where the leak sounds the loudest and hope for the best," he said. "Then we continue until we find the exact spot of the leak."

Some other obstacles to the plumbers looking for leaks include wooden floors, which don't transmit sound as well as concrete does.

"The leaks under wooden floors are pretty hard to find," Knell said. "But we have an ultrasonic microphone that picks up the sound of high pitched leaks better, so we have a better shot at listening for leaks through wood floors."

Another problem can develop when plumbers shoot air into the water lines to try to detect the source of the leak.

"Sometimes we'll dislodge some of the calcium that's built up in the line and it will plug up the leak," Knell said. "We have had situations like that where the water line stopped leaking for six months, and then started leaking again."

Knell said one of the most difficult problems he has had to deal with is odor leaks. Usually, he would do a smoke test where he pumps smoke into the drain line and detects where the leak (and odor) is coming from.

"I had a case where the people had bought a house, remodeled, and found that a nasty smell had developed in the master bedroom, so bad they couldn't use the room," Knell said. "They had a water leak in the adjacent bathroom and called us in to investigate. We found the leak and when we dug it up we found an old termite nest under the slab that had begun to rot and smell."

Knell laughs for a moment. "But most of our work is pretty routine and boring," he added.

Bob Cruz of Cruz Brothers Locators in Scott Valley, Calif., has been in the leak detection and utility location business for more than 20 years and has ten employees. Half of his work is in leak detection, and of that business, half is residential.

"The typical residential call is to locate a water leak under a concrete slab floor or in a concrete slab floor with radiant heating," Cruz said. "Sometimes we'll find a leak between the meter and the house and other times we'll be called out to handle irrigation problems."

The chief cause of under-slab water leaks, Cruz said, is usually corrosion in the pipes, especially if they have been in the ground for 20 or 30 years.

"Most of the leaks we find are ones that have corroded from the inside out," Cruz noted. "Often copper piping has impurities in it, that when it's mixed with chlorine or minerals in the water, causes scabbing inside the pipe. That's usually where we find the leak. The outside of the pipe may look fine, but inside there is a large mineral build-up."

A lot of things can be going on with a water pipe under the concrete to cause a leak, Cruz pointed out.

"If it's buried in dirt or gravel, the pipe may be touching the concrete," he said. "So you have to determine where the leak is coming from-the top, side or bottom. Plus you have to figure out if the leak is under water or if it is migrating, and if it's under water, it could produce a bubbling effect because of water pooling around the pipe."

Cruz added there are many things to consider at a leak location and each one will be different.

"You'll want to locate the pipe and have a good idea of its depth and alignment," he said. "And when you have to make a hole, you want to minimize the site of the excavation."

Cruz uses a rule of thumb of cutting a hole the same diameter as the depth of the pipe.

"The deeper the pipe gets, the bigger the hole will have to be in order for you to get your arms and tools into the hole to fix the leak," he said. "I use the same rule of thumb when pinpointing the leak. I want it to be within the width of that hole."

Cruz has been listening to leak sounds for a lot of years and believes that while the equipment offers filtering options, the operator must eventually mix the sounds in his head and make a decision about the location of the leak.

"Experience helps, but it's important to know the kinds of sounds you're listening for and how to filter out the other sounds," he said.

Another technique that Cruz uses is to place several listening devices around the leak. If they all indicate a leak location in the same area, you can have some confidence in their results, he noted.

Marty Silverman, marketing manager for General Wire Spring Co. in McKees Rocks, Pa., said the number one issue with leak detection deals with amplification of the sound.

"If the unit doesn't filter out all the other noise, traffic, air conditioners and air compressors, then it will be hard to hear the leak," Silverman said.

Silverman pointed out that General Wire Spring's Gen-Ear uses a digital spectrum analyzer to combine 16 frequencies to eliminate extraneous sound, allowing plumbers to hear the sound of the water leak.

"Gen-Ear is designed to be used by the average plumber, and not only by the leak specialists," Silverman pointed out.

Casey Pelton, vice president of sales for Metrotech Corp. in Santa Clara, Calif., noted that plumbers should try to match the leak detection equipment they will use to the kind of jobs they want to get.

"There is a huge range of instruments available, from simple to very sophisticated," he noted. "If you want to target a certain type of job, look for the equipment that will serve you best, whether it's for residential work in high end homes or commercial contracts with municipalities."

Damon Maniscalco, field supervisor for ProServ Plumbing in Costa Mesa, Calif., said his number one type of client is a homeowner's association comprised of residential slab homes.

"We do a lot of leaks under slab homes and reroute 90 percent of the leaks through the attics of single story homes and the walls and ceilings of two story houses," he said.

Many of the customers who employ ProServ Plumbing are litigation attorneys who want a sample of a leaking pipe as evidence in a lawsuit.

"That's the main customer who wants to dig up a floor," Maniscalco said. "But sometimes cost is a factor. Perhaps if the leak is in the middle of the floor it would cost less to dig and fix it rather than go the overhead route. Overhead, you have to pay for the cost of the drywall, taping and painting, as well as rerouting the pipe itself."

Maniscalco said that if you're a plumber, you'll want to learn the leak detection field because it usually is a high ticket area.

"It opens up more avenues for you to increase your business," he said. "It definitely will increase your earning potential and there certainly are a lot of leaks out there that need to be fixed."

Leak detection companies around the country seem to be quite busy, according to Carson.

"Some of the leak detection plumbers can be running two to three weeks behind in servicing leak jobs because there is so much business for them," he said.