THIS IS THE LAST installment of three on leak detection. My two previous columns (July, pg. 18, and August, pg. 28) covered the search for a pinhole leak that had corroded four boilers.
Although I didn’t have to resort to my third method, it consists of an ultrasonic leak detector like the type used to locate leaks in refrigerant or compressed gas systems. It requires you to pump compressed air or another denser gas such as carbon dioxide into the system; this produces a high-pitched squeal when it escapes from the pipe.
I have seen people using this method and a conventional engine-type stethoscope to locate leaks. You can spend a lot of time on your hands and knees for naught. Most of the new electronic leak detectors have extension handles on them to keep the operator in an upright and comfortable position.
The only problem with this type of device is that you typically have 4 in. of sound-deadening concrete between you and the leak. While it doesn’t work perfectly in every case, it can come in handy as a backup method if all else fails.
Although I’ve never personally used this last method, I understand that you can charge the system with a benign gas, such as helium, nitrogen or carbon dioxide. Using a gas-sniffing type of detector, you can locate the leak through the concrete. Since I’ve never used it, I’m not sure of the accuracy of this system.
I see that General Pipe Cleaners now offers a leak-detection system that is similar to the Metrotech detector. The unit is called the Gen-Ear. It is an audio-type of detector with a ground-mount microphone and a contact mike along with a 16-channel analyzer. More information is available at www.generalpipecleaners.com/whatsnew. html.
For more information on the Metrotech line of leak detectors go to www.metrotech.com/Content/htm/pdfs/hl6000.pdf.
To locate leaks in their water mains, municipalities use a more expensive unit called a Doppler leak correlator/detector. This unit works on the principle that sound travels through different types of pipes at a constant speed. It has two “listening” devices. One is clamped to the subject pipe at point A, and the other is clamped to the pipe at point B.
Provided that you know exactly where the line runs, this device can tell you exactly where the leak is located. It gives you a reading in feet and inches from point A and from point B. Again, the problem with this device is the need to know exactly where underground lines are located. It weighs in at around $30,000, but if you plan to go into the leak detection business, it is a must-have tool. More information can be found at www.utsleak.com/sales/ leak_locators.htm#lc2100.
One of the Dead Men, my father, told me about a method that I’ve never had occasion to use. He used to tell of “the old guys” using oil de menthe, which is an extremely powerful mint odorant. He said they would pump it into the suspect pipe and then crawl around on hands and knees until they caught a whiff of the strong mint odor. No wonder they’re all taking dirt naps and pushing daisies, eh? Of course, they also liked to use a brace and bit to drill through wooden framing members too! And they wonder why a plumber’s knees, elbows and shoulders fail at such a high rate.
Before you plop down a few thousand dollars for any given device, I would strongly suggest that you ask for a demonstration and take a few for a test drive under actual working conditions to make sure that you are comfortable with the technology available. Most manufacturers reps will be more than happy to come to a jobsite and give you a demonstration.
Now, about the mop and the old cat. If the subject floor is tile over cement and the leak has been occurring for quite a while, you can mop the floor with cool water and note where the floor dries first. This indicates a higher floor temperature that would cause the water to evaporate more quickly. The major drawback of this method is that it doesn’t work on carpeted floors.
Old cats have this uncanny ability to find the warmest spot to relax and clean themselves. Just turn the cat loose and wait for him to find the warmest spot. The disadvantages of using an old cat is that they are usually lazy, and they may not necessarily find the warmest spot but instead may opt for the first warm spot they find. If I were you, I’d invest in something other than a mop or an old cat.
In general, leak detection can be a frustrating game at times, and it can be a rewarding at times. It all depends on your level of skill, knowledge of piping practices and belief in technology. But it sure beats crawling around on your hands and knees with a screwdriver held up to your temple!
Happy Leak Hunting Hydronicing!
Mark Eatherton is a Denver-based hydronics contractor. He can be reached via e-mail at [email protected] or by phone at 303/778-7772.