Heat expansion noise

gfrbrookline

I raised a problem radiator about 1/4" on the supply side and 1/2" on the vent side. I no longer have water hammers but now have knocking sounds coming from the pipes.

Do the joints need time to settle out to the new radiator height? Haven't had this issue before when I raised radiators to correct pitch of either radiators or run outs.

ethicalpaul

Maybe the slope problem or “valley” got moved and you’re hearing water hammer farther down the pipe.

Or your work increased tension (removed free play) in the pipe and it is expansion noise.

Is this an upstairs radiator or can you listen/observe in the basement?

mattmia2

In addition to water hammer somewhere new it could be that it is now binding against a hole in the framing and sticking ans slipping as it expands and contracts. Depends on the sound of the "knock".

pecmsg

Lower it a1/4” and see what happens.

gfrbrookline

@pecmsg that's what I did and it fixed the problem. Good call.

gfrbrookline

I know a lot of people here recommend pocket change for shims, I like cedar blocks since they can spread the weight of the radiator foot over three floor boards to reduce sinking on one board.

BobC

I used plywood strips about 1-1/2" wide (adjust length to fit radiator depths), they are cheap and can be stained so they don't swear at the floor. You can use different thicknesses to correct slope issues.

Bob