I live in an apartment building. Time to time, sound like flushed water going down in pipes come from our bathroom, likely when higher floor neighbors just finished using their toilet.

Is there a way to diagnose and fix this noise? Thanks!

  • 2
    You've already diagnosed the problem. Fixing the noise will be next to impossible unless you can rip out the drywall and heavily insulate the pipes. Even then, the improvement could be minimal.
    – JACK
    Jun 8, 2021 at 12:40
  • 1
    This probably is a condition you will have to accept. In the US cast iron drains are used in some runs in multistory buildings to dampen sounds of draining water even when most of the runs are PVC or other plastic. Jun 8, 2021 at 12:46
  • 2
    @JACK comparing two houses (one of them mine, and that's had a new toilet fitted) there can be a real difference in sound. Mine has the boxing in made from a double layer of plasterboard (drywall) with some rockwool insulation in the wooden frame, not against the pipe, and I managed to drop a chain down there to pull some network cable, and is quiet. The other has a much thinner construction. I don't know exactly what, but knocking on it it sounds much more hollow than mine. There's certainly room for improvement
    – Chris H
    Jun 8, 2021 at 13:58
  • 2
    I agree with Jack, sometimes it is impossible to dampen the noise from a drain in a multi story building, we tried insulation even moving the lower floor toilets to allow 2 more inches of space and insulation but the building owner was never satisfied but did not want to take the chance to decouple the pipes as this increases the chance of leaks.
    – Ed Beal
    Jun 8, 2021 at 14:28


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