Does cast iron p-trap sweat?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by DavidTu, Jun 23, 2011.

  1. DavidTu

    DavidTu Member

    Messages:
    239
    Location:
    Seattle, WA
    Did a test yesterday of a tub installation. Ran cold water until it overflowed, then let out the drain. Did not detect any leakage. Great. But today, while adding a strap I noticed my hands got wet. I'm wondering if this indicates maybe I did have a leak or is it likely that the p-trap is just sweating?
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,051
    Location:
    Cave Creek, Arizona
    Anything will "sweat" if it is cooler than the "100% relative humidity" point for the moisture in the air. BUT, if the trap is that cool, everything else in the area should be also, so there should be other areas of condensation.
  3. plumber2011

    plumber2011 Expert Plumber

    Messages:
    70
    Location:
    Boston, Massachusetts
    Hi David,

    Simple enough to find out, right? Fill the tub to overflowing again and then drain the tub again...use warm water this time. Use a flashlight to check around all seals at the tub waste and overflow assembly. Sounds like a leaker to me...I hope not!!

    Good luck!
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,268
    Location:
    New England
    After a day, it would be at room temperature, and unless everything else was wet from condensation, it's likely a leak.
  5. DavidTu

    DavidTu Member

    Messages:
    239
    Location:
    Seattle, WA
    It did turn out to be a leak. I tightened the slip joint again (had to use pliers handles on the little tabs on the nut to get enough torque) but it seems to be ok now. There was also a drop of water in the basin area, so I also tightened the basket nut up too. Geberit had recommended redoing the silicone for the basket seat but I wasn't able to pry it up so thought I'd try tightening it up and that seems to have done the trick.
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