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Old 07-07-2009, 02:36 PM   #1
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Hot water leak under slab

I've got a hot water leak under my c.1955 slab. My oil burner kickes on every 60-70 minutes and you can hear the pipes "whining" when you're in the bathroom. When I turn off the hot supply, the "whining" stops and the leak detector stops on the meter.

You can feel the warmth from the pipe's path under foot and it takes awhile for the slab to cool down once the water supply is cut. My question is: Does it stand to reason that the leaking area would be the first to get warm? I bought an infrared thermometer and I was hoping to pinpoint the leak site before I tear up my hardwood floor. There is absolutely no hint of moisture in the area I am targeting.




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Old 07-07-2009, 09:00 PM   #2
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This is a good guess but not foolproof.

Since you can feel the path of the pipe once it heats up, try this. Turn the water back on but don't use any hot water for several hours. Feel for the warm path and where the path ends is probably where the leak is. (Hot water won't progress past that point when none is being used.)


The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.
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Old 07-08-2009, 10:53 AM   #3
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Thanks Allan!

Does anyone know if a Stethoscope might help? It has to go through a 4" slab.

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Old 02-16-2015, 11:15 AM   #4
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I don't think the stethoscope is going to be enough here.
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Old 02-16-2015, 12:29 PM   #5
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Not going to do much good location that one leak.
By now that old plumbing is paper thin and needs to be rerouted through the walls or over head.
When posting in forums, letting us know your location will help others give better feedback/advice/solutions to your questions
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Old 02-16-2015, 05:23 PM   #6
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Ayuh,.... After playin' with my point, 'n shoot temp sensor on my radiant floor, I'm thinkin' you oughta be able to find yer leak, within' a foot or two,....

There should be a Hot line right to the leak, 'n then spreadin' lower heat,...
or heat goin' wherever it's perkin' into the soil,...
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Old 02-16-2015, 08:28 PM   #7
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Been there done that didn't work. You would need a thermal image camera.
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Old 02-17-2015, 01:23 AM   #8
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When there was a hot water leak under our concrete slab, I replaced it with PEX in the attic. That worked since it never freezes in our area. Was a LOT easier than trying to find the leak under the slab, breaking through 4 inches of concrete and disrupting our home for a long period.

Besides, even if the leak is found and repaired, my guess is that another leak will probably happen again someplace else within a couple of years. Because the copper hot water line under the slab is now marginal IMO.



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