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Hot water pipes under slab - warm spot bad?

amin1992amin1992 Member Posts: 26
edited January 21 in Radiant Heating
Hey guys, sorry if this isn't the right section to post and if this is a silly question. I'll try to be short.

Bilevel home heated by hot water baseboard. 2 zones and the lower level has the hot water pipes going under the concrete slab.

Anyway, I noticed in the laundry room in lower level that one tile is warm on the feet while the others are icy. I figured this was just heat radiating from one of the pipes.

However I was reading random discussions and saw that could be a sign of a corrosive water leak under the slab. Ah!

However, my boiler has a water pressure gauge and it hasn't moved from its normal range all year. Conversely, I had a pinhole leak in one of the hot water pipes a while back that was emergency repaired, and when that happened the pressure quickly dropped within the hour.

Is it possible a part of the hot water pipes is just radiating some heat into the tile? I don't know exactly where the pipes are situated underground but it's entirely possible some copper pipe is traveling under that tile to another room in that zone.

Thanks for the tips guys

Comments

  • Jolly BodgerJolly Bodger Member Posts: 209
    It could be that the pipe is close to the surface at that tile. It could also be a small leak. If you are not loosing water then don't worry about it. If you boiler has an auto-fill and it is working, you will not see a small leak drop the pressure. It would have to be turned off and watch for pressure drop. If you are loosing pressure then the warm spot is highly suspect.
  • STEVEusaPASTEVEusaPA Member Posts: 4,308
    Shoot it with a thermal imaging camera
    steve
  • amin1992amin1992 Member Posts: 26

    It could be that the pipe is close to the surface at that tile. It could also be a small leak. If you are not loosing water then don't worry about it. If you boiler has an auto-fill and it is working, you will not see a small leak drop the pressure. It would have to be turned off and watch for pressure drop. If you are loosing pressure then the warm spot is highly suspect.

    That's what I'm hoping! My boiler does NOT have an auto fill. I don't know a lot about the terminology and such but when I had that emergency leak way back, the tech that came out taught me a bit about the system. There is a gate valve to manually fill the system with water (increases pressure) and looks like the only way to remove water (decrease pressure) is through the two zones' purge valves (also gate valves) or if there were a leak. So that's good news!

    Shoot it with a thermal imaging camera

    Good idea. I suppose that would show if the heat is concentrated in a line (pipe) or if it's spread (like a water leak) right?

    Thanks all for the advice
  • STEVEusaPASTEVEusaPA Member Posts: 4,308
    Yes, when the loop is heating up, you'll see the lines of heat. If you see a blob, that's a leak.
    Also helps you map out where to drill to avoid damage to the rest of the tubing.
    steve
  • amin1992amin1992 Member Posts: 26
    edited January 22
    Just wanted to report back. After doing some research, I'm kind of stumped!

    Turned the heat off downstairs for over an hour. Checked a few of the hot water baseboard pipes: cold to the touch and laser thermometer says 66F, but tile still warm.

    Then I thought maybe it was a leaking domestic hot water pipe. However, tracing back to the boiler I found that all domestic hot water is ran between the first/second floor, so it must be plumbed through the ceiling in the lower level, and therefore not under the tile.

    And just to be sure, I had my wife not touch the water for an hour and a half, and checked my well's pressure gauge before and after. It didn't move at all in that time, so no water leaking throughout the house... I filled up half a glass of water and the gauge moved a tick so if there is a leak then it's less than half a glass which seems unrealistic...

    I'm at a bit of a loss. After all this, the warm tile measured 75F haha! No clue where this mystery heat is coming from but it doesn't seem to be a water leak anywhere, so I'm not going to worry I guess.

    Thanks all
  • IcarusIcarus Member Posts: 105
    Fleer thermal camera image might be very informative.
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