I bought a quite old house, and I found on the attic a thing that's part of the central heating, and it's leaking water. Not a lot, but enough to soak through to the floor below.

Pictures: From above 1 From above 2 Close up.

I can't figure out what the thing does, as the water just runs from sideways to downstairs.

Is this something I can fix myself, or should I get a plumber?

  • It looks like a pressure relief valve to me. Try taking it off and cleaning it. Apr 28, 2014 at 15:55
  • More important than cleaning it would be to find out why it is opening - it could very well be that the system is running over pressure and the value is operating as designed.
    – Comintern
    Apr 28, 2014 at 22:31
  • Thanks for the help, I'll have someone more professional than me diagnose first, since that'd be safest
    – Tominator
    Apr 30, 2014 at 7:47

1 Answer 1


It is an automatic air vent that is supposed to allow air to escape from the heating pipes. It should not be leaking water. From the looks of it, it is definitely defective and should be replaced. I recommend a plumber.

  • You were correct, and it's replaced (something that should happen every few years because the top part could get dirt in it and be stuck). Also, on the floor part, there should have been tape to prevent rusting and water going into the concrete..
    – Tominator
    May 7, 2014 at 9:19

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