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Exhaust Pipe Ticking Noise

I have a natural gas hot water heater with a power vent that connects to a 2 1/2" diameter PVC pipe. The pipe has a vertical run above the tank of 3 feet and then a horizontal run of 12 feet where it exits the house on the west side.

Our bedroom is right above the exit point. Often during the night, usually between 4-6 am, I hear a ticking noise at the exterior wall loud enough to wake me up. It starts about once every 5 seconds and
gets louder and faster to about once every second. After a few minutes, it stops but then of course I can't get back to sleep.

I've put felt tabs on the pipe where it was touching the joist and a towel under it where it was sitting on a cross support. I put batt insulation above it between the joists and foam insulation around
the pipe itself. I even put insulating tape on the part that sticks outside of the house. I also tried lowering the water heater temperature. The house is only 8 1/2 years old and we've lived here for 5 1/2 years with this problem.

I'm thinking of rerouting the pipe to exit the house on the south side under the deck. It would mean doing a horizontal run of 3 feet east and 6 feet south in addition to the existing vertical run. Is it OK to exhaust under the deck? Does anyone have any other suggestions?

Re: Exhaust Pipe Ticking Noise

You have probably eliminated every possible place where the pipe could rub, except one: the hole thru the wall.

If you immobilize the pipe at that point, any movement due to expansion and contraction of the PVC will happen back at the point where the pipe turns from vertical to horizontal, where it can move freely without scraping and squeaking against anything.

Re: Exhaust Pipe Ticking Noise

I did check out the hole through the wall. I tried to shake it vigourously and didn't see any movement. There is plenty of caulking all around it. I even jammed up a piece of 2x4 (with pieces of felt on either side of it) between the pipe and the nearest joist just to be sure.

Re: Exhaust Pipe Ticking Noise

You can also try slipping something like thin sheet metal rolled into a sort of sleeve to separate the pipe from the wood. This allows the pipe to move without making the noise.

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