I'm getting a strange repetitive clicking sound out of a new construction tall DWV pipe.

It is in a 4 level house, including the finished basement and attic. The pipe goes straight up from the basement's concrete floor to the attic floor (about 30') where it then splits into two 2" pipes. One is connected via a sanitary tee to a 2" horizontal drain from the top levels kitchen sink, and just above this, the 3" reduces to 2", goes through a nearby exterior wall of the finished attic and then through the roof as a vent.

The third and fourth levels of the house have drywall up already, but the first and second level are still at rough framing, so I'm hoping there is a way to fix the sound without having to remove any drywall. Unfortunately, the drywall makes it harder to pinpoint the sound on the upper levels.

In fact, the clicking is very hard to pinpoint in general. It sounds equally loud from all three levels that the pipe runs through. It also always sounds like it coming from above, no matter what level you are listening from. Only when you are in the attic does it sound like its coming from below.

At first, I thought maybe it was the sound of dripping water, falling 20' and hitting the bottom of the stack below the basement floor and reverberating back up the stack. However, if I put my ear to the pipe I can hear what is distinctly flowing water that sounds like a steady stream, rather than discreet drops that would make the rhythmic sound I'm hearing. The sound is also much louder than falling drops of water would make.

I'm guessing it is coming from the framing because the clicks I hear sound more like creaking wood, but I could be wrong here. It is hard for me to imagine how water flowing through the drains would cause enough expansion or contraction in PVC to move the framing, and if so, why does it occur rhythmically.

Does the noise occur with the draining of just hot water or is there also noise with cold water? What material are the supply pipes?

>if I put my ear to the pipe I can hear what is distinctly flowing water that sounds like a steady stream

You have a waste pipe connected to only one sink and one vent in the attic. If that sink is not draining, and you hear a "steady stream" then you are hearing either the wind whistling past the vent or sounds conducted from below, not above.

>why does it occur rhythmically

It is a rhythmic sound from somewhere down below. Possible sources include timers, water heaters, recirculation pumps, appliances and anything with power near other drains. Try turning off the power to this (unoccupied?) house, see what happens to the clicking sound. If you hear it with both the power and water turned off, it's coming from underground. Maybe your house was built on a native american burial ground?



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it most likely IS expansion.
not the wood expanding but the PVC pipe expanding.
the thing is that it will only make noise when hot water is running thru it.
so for now you will have to do some detective work.
pay attention when fixtures are run to see if you can determine what makes the noise and what doesn't.

Packy I think is referring to plastic pipes that expand when hot water is drained. You must make sure that there is clearance around all of these pipes when inside a wall and through the 2x4" plates at each penetration all the way through the roof. We used to use Felt strips for sound isolation. Hope that makes sense.

Just thinking to myself that the lack of a proper wet wall makes it much more difficult to keep the pipe off framing. Nowadays they cram a 3" pvc pipe into a 2x4 wall. A two-by six wall would allow for larger opening at the floor, and insulation to quiet the noisy pvc. Sorry......don't want to hijack your thread. Just lamenting where things have gone.

good/best practice versus minimum code compliance

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

paul, while 3 inch pipe will fit into a 2 x 4 wall the fitting OD is 4 inch.
i have done them where the wall was 2 x 4 with strapping nailed on to make it 4 1/4 inch thick.

Probably an 800k house too. Running right down the living room wall. It's just lovely when you have guests over, and someone flushes the upstairs toilet. It's nice to see their faces as they look for a place to run to.

If the builder wants quiet pipes they will have the plumber install cast iron drops from upstairs.
I was in a 600K home a few months ago with this same problem.