A new way to find leaks

Device tracks current to find holes in vinyl

Attested by the number of better mousetraps on the market, there’s something about people with an engineering mentalitythat makes them seek out a better solution to any problem.

And so it was with Chris Alm, a 75-year-old retired electrical engineer in Wallingford, Conn., who some years back was having problem locating a pesky leak in his backyard vinyl-liner pool.

We all know that if you are losing more water than normal evaporation would produce and if you have a big gash in your pool wall, even your not-too-bright second cousin can deduce the exact point of the problem.

But if you’ve been around the pool business for any length of time, you also know that very few leaks are quite so noticeable. Most of the time, they tend to hide in the underground plumbing, skimmer throats, light niches or other fittings or in tiny, nearly invisible cuts in vinyl or cracks in the plaster.

Alm knew that he had a problem somewhere in the pool vessel itself. But he couldn’t see it and he didn’t want to have to dive the poolas it were. So he began putting his engineering training to work to solve the problem.

Using his knowledge of electricity, he figured that if he placed an electrical charge into the water, that charge would then seek to make the least resistant connection to ground the nature of electricity, after all, is always to follow the path of least resistance.

The electrical current flow would then create a path that he could track by measuring the voltage potential at different points in the pool and translating that information into an audible sound. That sound, Alm theorized, would increase in frequency as the voltage differential was increased.

The idea for the better mousetrap was born and Alm then set out to create a device that could track this sound. His device worked, solving the leak-locating dilemma on his home pool. At the same time, Alm thought he had come upon an idea that could be used by others.

About four years ago, he brought his raw idea to Lance Anderson of Anderson Manufacturing, a St. Paul, Minn.-based manufacturer of pressure testing plugs and other leak-locating devices and accessories. After working out a few bugs in the initial design, Anderson has indeed developed Alm’s idea into a marketable concept the LeakTrac 2100.

Obviously, the unit had to be made so that the electrical charge being put into the water was safe enough to be used. Another problem with the initial design was one of isolating the ground areas in the pool like the pool light niche so that the device would react only to leaks.

Since its introduction at the National Spa & Pool Institute International Expo last year, a limited number (about 100 units) have been sold across the country. Anderson limited distribution so that the company could better monitor early results. So far, the results have proven to be excellent, and Anderson is optimistic that they have a product that could revolutionized the vinyl-liner leak-locating marketplace.

The LeakTrac 2100 consists of seven components, all of which are contained in a protective plastic carrying case.

1. The Signal Processing Unit a 5½-by-5½-by-1-inch gray plastic case that contains two 9-volt batteries and circuitry to convert input from the sensor probe into the audible clicking sound used for leak finding. An adjustable strap allows this unit to be conveniently worn around the operator’s neck. The front face of the component has a power-amplification control knob, which turns the unit on and allows the operator to select the degree of amplification. Another knob allows for adjustment in the rate of clicking to a desirable level once the amplification has been selected. There’s also an LED low-battery indicator, which warns the operator when the batteries need to be replaced. The back of the unit has three input/output jacks, one for accepting the phono plug from the sensor probe, one for locking the connector from the booster patch cable and one for accepting the headphone jack.
2. The Power Booster a 3-by-6-by-1½-inch black plastic box that contains the AA batteries and circuitry required to provide an appropriate voltage between the pool water and ground. The component has three input/output jacks, allowing connection from the booster batch cable, the ground cable and the input float cable. Power is turned on and off with the signal processing unit’s power knob and another LED low battery indicates when batteries need replacing.
3. The Sensor Probe a T-shaped PVC configuration that picks up the current flow signals from the water. The probe attaches to a standard telescoping pole to allow surveying all parts of the pool. Twenty feet of wire extends from the probe and attaches to the signal processing unit. Probe extension caps cover the ends of the probe to reduce random signal readings that result from water flow over the electrodes.
4. The Input Float a brass plate attached to a block of foam that floats in the pool and puts the electrical charge into the water. A length of insulated wire connects the float to the power booster. A lead weight provides a means of anchoring the float in its desired position.
5. The Ground Cable a clamp used to make a connection to ground. A length of insulated wire is used to connect the ground to the power booster.
6. Booster Patch Cable an 80-foot length of 2-conductor wire used to connect the power booster to the signal processing unit.
7. Headphones a set of standard headphones that plug into the back of the signal processing unit.

1. The difference in conductivity of the pool shell in comparison to the point of low resistance. The LeakTrac 2100 does not work well in concrete pools because the concrete itself conducts electricity to the ground as well as a leak would.
2. The number of points of low resistance in the pool. Because there is a limited amount of charge going into the pool, the strongest leak track will be produced when there is only one path for the charge to connect to ground.
3. The relative conductivity of different points of low resistance. A highly conductive connection to ground will take more current flow and produce a stronger signal than a less conductive one in the same pool. Leaks are often not the only low resistance paths from inside a pool to ground. Other metallic connections such as light niches, fitting screws and even grounded equipment like the pool heater —may produce leak tracks.

For best results, you’ll need to create the strongest possible leak track, while eliminating or disregarding other connections to ground that are not leaks.

Before using the LeakTrac, Anderson recommends that service professionals first confirm that there is indeed a leak in the first place. Generally, anytime that a pool loses more than ¼-inch of water a day, a leak should be suspected. But evaporation rates vary in different parts of the country and can be greatly affected by temperature, winds and other atmospheric variables.

For this reason, most leak-locating specialists recommend using a simple bucket test to confirm existence of a pool leak. To perform the test, place a bucket of water in or next to the pool, mark the water level in both the pool and the bucket, and leave them for 24 hours. If the water level in the pool drops more than the bucket’s water level, there is a leak.

Next, you’ll need to pressure test the plumbing lines and repair any leaking pipes. Using this method, attach a pressure testing plug to the suspected leaking section of plumbing, plug any other openings in that section, attach a garden hose to the tester and add water to the plumbing until the gauge reads 20 pounds per square inch. Then turn the water off.

If there is no leak, the pressure will remain constant. If the section is leaking, the pressure will drop. After confirming a specific section, you can then add air to the lines with a small compressor to better pinpoint exact leak areas.

The compressed air is added to the leaking section of plumbing at a constant rate to maintain the 20 psi reading. When air reaches the leak, you will notice a dramatic drop. It will require much more air to maintain 20 psi.

Now add a little water along with the air, to maintain the 20 psi. This air/water mixture will create a noise that can be heard using a listening device such as the geophone. As you near the problem area, the noise will increase. Move away and it decreases. In this manner, it will soon become clear when you are directly over the leak.

Once you have determined the position of the plumbing leak, you will have to expose and repair it. If the leak is located beneath dirt, your job isn’t too bad. But if it is under the pool deck, that may be a different story. And depending on your expertise and licensing, you may need the help of a professional leak locating/repair contractor. Finally, you need to dye test around the lights, return fittings, skimmers and stairs to assure that these areas are not leaking. A common structural leak-locating tool, an eyedropper filled with water coloring, allows you to squirt a little fluid near the affected area and see if it gravitates toward the suspected leak.

Again, if you locate the leak in these areas, you’ll need to expose and repair it using patches, glues and epoxies. With these locating chores completed and fairly convinced that a structural leak is causing the problem, it’s time to put the LeakTrac 2100 to work on a vinyl-liner pool.

Following the manufacturer’s directions, make sure that the pool circulation system is shut down and that the pool is filled to its normal level to assure that all leaks are underwater.

Remove automatic cleaning devices that may become tangled in the LeakTrac cables. Remove any connections from inside the pool to ground, including ladders, thermometers, vacuum poles or wet pool covers. If a ladder cannot be removed, you should place a plastic trash bag over it to insulated it from the pool water.

Cover the pool light with the light cover available with the unit. The special Anderson cover is designed to be suctioned against the pool wall for effective insulation.

It may be necessary to plug return lines and skimmer fittings with nylon test plugs to eliminate possible current flowing back into the ground equipment. Main drains can be covered with a 5-gallon bucket (filled with rocks or cement). But in most cases, plugging the fittings and main drain is not necessary. Instead, you can simply eliminate the relatively weak signals that they generate.

To use the LeakTrac 2100, you’ll have to locate a good ground connection, such as a ladder anchor socket, diving board anchor bolt or pool coping.

If you are using a conductive T-pole, it is important that the pole itself not become a connection to ground as you look for leaks. Be careful not to touch the pool to the pool coping. Also, be sure that to wear rubber-soled shoes or insulating gloves.

After the unit is fully wired, place the probe into the water and power up the unit to the highest setting (100X). Then adjust the sensitivity knob to produce a consistent clicking rate of approximately 2 to 3 clicks per second.

Rotate the probe to determine where the most rapid rate of clicking is heard. The black striped end of the probe will point to the portion of the pool where electrical leakage is occurring. If there is no variation in the clicking rate, simple move the probe a few feet and repeat.

Then move the probe in the direction of the highest clicking rate, occasionally turning the probe to assure that you are moving in the right direction. As you near the leak, the intensity of the clicking will become increasingly rapid, turning from clicking into what has been described as a high-pitched whine.

When the unit moves from the whine to a chattering or stops making any sound at all, the signal it is receiving is too high for the power setting. At this point, turn the power knob down to the lower settings (10X or 1X) to allow for pinpointing the leak.

Most leaks are discovered as you are moving the probe in the direction producing the higher pitch and then all of a sudden the signal stops. This indicates that the probe has passed over the leak and is now pointing away. Turn the probe around and carefully examine the area just passed.

Because a small electrical charge is being placed in the pool water about 0.1 amp there is a risk of minor electrical shocks being felt if you become a connection from the pool water to ground. This shock should not be harmful to persons without medical conditions, but some common-sense safety rules should be followed:

• Never contact both the pool water and the ground while the unit is turned on.
• Always wear rubber soled shoes.
• Never allow swimmers in the pool while using the unit.

We had a pool that we just couldn’t find the leak,Thatcher says. We put it to use and, by golly, we found it. Turned out that it was the size of a pencil head, and right on the seam.

Bob Muehlbach of the Pool Outlet in Olathe, Kan., says that his service crew has had success with the new leak locating device since acquiring it June 1, especially in locating those annoying little holesin liners.

And, as side benefit, Muehlbach says that his company has sold a couple of liners because of LeakTrac. We had one pool where we found 20 little holes spread all over,he says. The customer realized that rather than spending a lot of time and money in repairs, he’d be dollars ahead just buying a new liner.

Leak locating has been one of the fastest growing segments of the pool and spa industry in recent years. We’ve witnessed companies develop franchising opportunities galore and have seen individual firms expand their service business by utilizing new high-tech devices and tried and true methods to pinpoint leaks anywhere in the pool or spa plumbing or structural system.

Now, thanks to Chris Alm’s better mousetrap, locating structural leaks in vinyl liners pools is also going to be considerably easier.