Hello and thank you for your reply.
I have a very loud and at times rapid tapping noise in the wall. The apt building is 2 stories high, I am located on the bottom floor (end of the plumbing line). 1 year ago the tenant (manager) moved above me - started adjusting radiator 4-5 times a day with a heavy tool often leading to some clanging. These are not large cast iron radiators they are built into the wall (tube-and-fin convector radiators ?)
Check out the sound: https://www.youtube.com/watch?v=kEGlqRcmPTI&feature=youtu.be - this is low sounding tapping and not as rapid as it gets... having issues posting new videos will update when I figure out Mac.
We have the same room layout, same radiator locations … 2 radiators located on the same wall, one in BR, one in DR . Hot water heating. I do not know if this is water-circulating-heating - I did not know what advertising/search tags to use - radiator tapping was not available. Main boiler in basement - plumber said it is hot water heating - no steam in pipes.
The tapping noise is located on the adjacent wall to the radiator. Tapping varies in location of wall, mid-wall or close to the ceiling and in decibel. When the manager adjusts radiators and I get tapping or no tapping. I have recorded the times of adjustment - that within 5 minutes of adjustment the tapping will either stop or start. Recently the plumber has had to fix a radiator leak in the managers apt. I went 18 hours without tapping – weather was freezing, she was not here to adjust the radiator. I do not have a decibel tester or a smart phone to record how loud it is but recorded it by video recorder.
Is the mid-wall tap or ceiling tap caused by different radiators?
If you turn the radiator part way do can you create tapping? I was told that partial radiator adjustment can lead to tapping and leakage.
Does turning on the radiator heat create the tapping?
Or, turning off the radiator heat create the tapping? The wall gets very hot making me think that it builds up in the wall.
Is there another fix besides opening up the wall?
The building owner does not want to fix expanding pipes which seems to be the issue – open up the wall. I have lived here for 24 years and this is a new issue since the manager moved in 1yr ago. The manager has flat out denied turning the radiator on and off and owner will not investigate. If the tapping can be caused by partial opening and closing of radiator it is an easy fix.
I have logged the time, dates, circumstances of tapping start and stop over the last 2 weeks. There is a lot of window opening and closing along with the adjustment I have no idea if she turns the heat on or off to get the tapping.