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Hidden steam leak between floors

I’m in a 1929 house with a one-pipe steam system in central Connecticut. We have what appears to be a steam leak from just underneath a radiator on the third floor, which is kind of a partially-finished attic. The only sign of the leak is a pat-pat-pat on the ceiling in the master bedroom below, on the 2nd floor, which is heard only during a steam cycle. In the room with the rad, there is no sign or sound of the leak, although its vent makes enough noise that it may cover the sound. I presume there is steam leaking just below the 3rd floor, and the condensate drips on the ceiling below. I program our thermostat to kick the temp up by 4 degF before we get up, and that’s when the pat-pat-pat gets intense (it wakes me up every morning). That 3rd floor rad is usually closed. When it is open, there is noticeably more dripping, but it drips plenty when closed.

The sound comes from the very corner of the master bedroom ceiling. I can’t see any water damage—yet. Closets wrap around that corner, so if I have to cut into walls (which by the way are plaster) at least there’s a fairly inconspicuous place to do it. But the sound comes from outside the closets, right at the corner of the bedroom ceiling.

I don’t know what would be causing this or how to go about fixing this thing. That 3rd floor room has an asbestos tile floor that I really don’t want to have to cut. Not that I’m eager to tear up walls and ceilings from below, either.

I’d appreciate any advice!


  • Putter-patter of little leaks

    It might be a pipe rubbing against some wood. If it were leaking, then I would expect some signs of moisture by now.--NBC
  • Jamie HallJamie Hall Member Posts: 6,660

    have you turned that radiator off?  You should turn it off with the vent (some turn off very happily by being turned upside down), not with the valve.

    As NBC says, that pat sound may be the riser expanding and rubbing on something, rather than water dripping.  That's very common.  And that's where I'd look first.

    It could be a leak, though -- the most likely places are around the valves -- but it is rare for steam leaks to condense enough to actually drip.  Like -- very rare.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • icesailoricesailor Member Posts: 7,265
    edited December 2013
    Leaks between floors:

    Buy a Ryobi "See-Snake, a cheap portable video cam system. Cut a hole in the ceiling under the sound and have a look. Sometimes you can rent them. Buying one is cheaper than paying someone to hack holes looking when it might just be a pipe rubbing. Water leaks of the heating variety usually don't take too ling before they show up somewhere.

    Ryobi Tek 4. For $100.00, you can't go wrong. An electrician friend bought one years ago and I borrowed it from him regularly. It works like a charm.
  • RedHerringRedHerring Member Posts: 3
    rubbing sounds way better

    Many thanks for the replies. Hadn't thought of a pipe rubbing against wood. I also thought it was weird for a steam leak to result in so much dripping, and why the dripping would be so loud given that there can't be much distance to fall between the floor and the ceiling. I can try to flip the vent over and see if it makes any difference, but actually when the valve is closed off the radiator seems pretty good and dead like it should be. If it is the rubbing it would still be nice to fix given the noise it makes but at least I wouldn't have to worry about things molding in the meantime. I'll see if I can get a scope up in there and see what's going on.

  • bustoff315bustoff315 Member Posts: 26
    Steam Leak?

    Do you have an automatic water feeder on your boiler? I would keep a close eye on the water level in the boiler before cutting anything open.
  • MDNLansingMDNLansing Member Posts: 297

    What kind of flooring do you have on the third floor? It might be easier to access it from the top.
  • vaporvacvaporvac Member Posts: 1,512
    Asbestos tile

    I think he posted in his intro : That 3rd floor room has an asbestos tile floor that I really don’t want to have to cut. Not that I’m eager to tear up walls and ceilings from below, either.

    Maybe there's a gap around the rad itself that you could get a scope down. I have quite a bit of a gap.
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • RedHerringRedHerring Member Posts: 3

    bustoff, yes the boiler has an automatic water feeder--why do you ask? Actually the system does seem to be losing water a bit faster than I'd expect, although there's no water counter so I can't quantify. Of course that could support the steam leak scenario (as opposed to rubbing) although there may be other minor leaks in the system.

    MDN, as vaporvac said it looks like asbestos tile on the 3rd floor, which is a drag--that's a rarely used room and I'd love to take care of this problem through that floor, but cutting into it I think is not an option. The gap around the supply pipe is pretty tight and I doubt I could get a scope in there.

    The sound still wakes me up every morning and continues for quite a long time (maybe 15 min. or so)--if I do find that it's due to things rubbing against each other, what can I do about it? Slip some lubricant between the pipe and wood? File down the wood?
  • Losing water or not?

    Valve off the auto feed and see if the water line drops. Verify the LWCO works first.

    Tell us how quickly the water goes.

    Afterwards to make sure it isn't the boiler, overfill the boiler and check for leaks there.--NBC
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