Locating under-floor leaks can be challenging

I received a frantic call the other day. The worried homeowner asked me if we replaced boilers. I asked him what made him think he actually needed a boiler replacement. s water running out from underneath the boiler! Thats a pretty strong indicator, I thought to myself. How old is this boiler, I asked? This is the third new boiler in four years, he said. It sounds like you have a leak in your heating

I received a frantic call the other day. The worried homeowner asked me if we replaced boilers. I asked him what made him think he actually needed a boiler replacement.

“There’s water running out from underneath the boiler!” That’s a pretty strong indicator, I thought to myself.

How old is this boiler, I asked? “This is the third new boiler in four years,” he said. It sounds like you have a leak in your heating system, I said.

“The only leak I can see is the big one coming from the bottom of my boiler,” he stated calmly.

Are you on city water, I asked? “No, I’m on a well,” he replied.

Are your electric bills exceptionally high, I asked? “Yes, but they’ve always been high. What are you getting at by asking me these questions,” he queried? I’m trying to determine whether you really have a leak or if there is some other reason these boilers have failed. This many boiler failures in such a short period of time is not normal.

“Why didn’t any of the other three contractors who replaced these boilers ask me any of these questions,” he asked? I guess the other contractors either didn’t understand, or they didn’t have your best interests in mind. I’ll be out within the hour and see what we can see.

Before I left the office I grabbed all of my leak detection equipment, including the hand-held infrared non-contact thermometer, my MetroTech audio leak detector, my Amprobe ultrasonic leak detector, a mop and an old cat. More on these last two items later.

Upon arrival, he took me to the boiler room, which was strewn with old boiler carcasses and melted down heat exchangers. The replacement boilers were a low-mass, copper-fin tube type of boiler. The heat exchangers were filled with hard water corrosion and the waterways were completely blocked off. This caused the heat exchanger to actually melt down and fail under fire. It was a sad sight to see.

The first thing I did was to disconnect the boiler, cap one line and apply air pressure to the other line. Within minutes, I’d confirmed my earlier suspicion. There was definitely a leak in the system.

A quick review of the construction method also confirmed my worst fear. The home was a slab-on-grade construction with three zones of hot water heat. All of the supply and return lines were below grade with slab penetrations where it came up to go into and out of the baseboard convectors.

I began the task of assessing and diagnosing the system, asking questions such as, have you ever noticed any exceptionally warm spots on the floor - the floor was carpeted everywhere except the bathrooms — to which the homeowner replied, no.

Have you ever noticed grass and flowers growing along the outside perimeter of the house during the winter, to which he replied, no.

Have you ever noticed an exceptional amount of condensation on the inside of the windows during cold weather, and he replied, no.

All these answers were telling me that the leak was not very large, and that the task of finding it (or them) was going to be a labor-intensive job. The sleuthing was also going to be hindered by the fact that carpet and pad were almost everywhere.

Oh, yeah, did I also mention that it was cold outside and getting colder by the hour? I didn’t have a lot of time.

My first suggestion was that we replace the boiler with a high-mass cast-iron boiler. My reasoning for this selection was based on the need to keep the system hot and pressurized in order to use the thermal infrared detector to locate the leak. This tool has been the most accurate of all my leak detection tools.

Once we got the boiler installed, I allowed his home to heat up again, and then showed him how to turn off the pump while keeping the boiler hot and pressurized. The theory behind this is twofold. Pressure, like heat, flows from high to low, always. By keeping the vessel hot and pressurized, the hot water would flow from the boiler directly to the leaks. The pump must be kept in the off position in order for this to work, hence the need for a high mass boiler that can be kept hot without a pump running.

Tune in next month as we continue our adventures in below-the-floor leak detection. Until then, Happy Leak Free 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.