Dripping Sound in wall - but goes away by pushing on wall?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by NoVAJustin, Sep 15, 2018.

  1. NoVAJustin

    NoVAJustin New Member

    Sep 15, 2018
    Northern Virginia
    Hello, I recently purchased my first home in Northern Virginia. It's a split level home, and in the basement level I mounted a TV on the wall that leads straight down from the kitchen above.

    When I run the dishwasher and it drains the water, I hear a dripping sound in the wall behind the tv for about 10-20 seconds. I was concerned that in mounting the tv, something may have happened to the drainage pipe. I ran the water and listened so that I could locate the drainage pipe. I then opened the wall a bit (only a few inches) and inspected the pipe and found no dampness or proof of damage.

    I can run the dishwasher again, and again I'll hear a dripping sound (coming from a few inches to the right of the drainage pipe it seems) for the same 10-20 seconds. The strange thing is, when I lean on the wall to hear it better, the dripping stops. When I stop leaning on the wall, it starts again. So then I tried with only a light push on the wall, and that makes it stop too. When I take my hands off the wall, it starts again.

    Like I said, we only just moved into this house, but there is no proof of water damage, the small part of the drainage pipe that I inspected looks fine, and the dripping only lasts for a short period of time.

    Any ideas?
  2. Chucky_ott

    Chucky_ott Member

    Apr 13, 2018
    Copper pipe contraction when the pipes cool and they rub against the studs/joists? The same thing happens in my house after running a bath. Drives me crazy because I always think there is a leak when I know there isn't.
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    It could be either the supply pipes expanding and jumping past a tight hole or clamp, or it could just as easily be the drainage pipes doing the same thing. PVC (and ABS) expand and contract a lot more than copper, and if they go through a hole or clamp that is tight, you'll get what I describe more as a clicking sound, but some could construe that to sound like a drip. This is one reason why cast iron drainage pipes is still considered a premium product...it tends to be silent. Plastic may outlive it, but the life of both is quite long. Plastic piping must be installed with expansion taken into consideration, or you will get expansion/contraction sounds where it is constricted. That constriction holds the pipe until the pressure gets too high, then it jumps a small amount until the process repeats...then, as it cools, it shortens, and jumps back in small increments.

    When you screwed the bracket into the wall to hold the TV, you probably pushed on the drain pipe, so it rubs as it expands and contracts. It may just be the wallboard is now tight against the studs where it wasn't before...it doesn't mean you put a hole in the thing, but that's possible...it doesn't alway leak right away...it can take years for the fastener to rust away and start to leak if you did puncture it.
  5. Michael Young

    Michael Young Active Member

    Sep 20, 2016
    North Carolina
    Sounds to me like you're just hearing the water inside the waste pipe. If you have a leak, YOU WILL SEE IT. You'll see discoloration on your sheetrock. You'll see some swelling at the floor. And if you look underneath, you'll see water dripping there as well (or puddles of water). Unless you see water or evidence of water. Ignore it. It ain't a leak
  6. Reach4

    Reach4 Well-Known Member

    Sep 25, 2013
    I expect that by pressing the wall, you are dampening the sound vibration transmission.
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