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.

thank you.

  • This sound is almost certainly due to pipe expansion in the walls or even in the radiator elements (expanding against the supports). This can happen any time the flow rate changes significantly, tho' it's usually most noticeable when the heat comes on after a period of quiet. But: if it's really a new issue, then something has changed in the flow patterns. Jan 5, 2017 at 16:53
  • thank you Carl - heard on rare occasion 2 yrs ago - this is now chronic. At times very loud and rapid escalating when the tenant goes to bed. I have posted a photo of what type of radiator it is in the next comment. Ty
    – catnip
    Jan 6, 2017 at 4:09
  • I guess the answer is "No" -- youtu.be/wT5ms2Nvpco
    – Hot Licks
    Feb 23, 2021 at 22:48

1 Answer 1


It sounds like you have hot water (hydronic) baseboard radiators, something like this:

Fin tube baseboard radiator

Tapping noises in these systems typically happen due to thermal expansion. The copper pipes expand as they heat up. If this expansion causes them to rub against floor/wall penetrations, or on parts within the baseboard radiator itself, you can hear a tapping or knocking noise.

Your video sounds similar to what I'd hear in a previous apartment that had noisy baseboard heat. Luckily, I've installed hydronic baseboard in my current home, and I'm happy to report that it can be completely silent if installed properly. You can also fix a noisy installation, but it will likely require access along the entire route to find and eliminate friction points.

If the noise only appeared recently, it's possible that (1) part of the system that was previously unused is getting used more and (2) changes to the system created a new friction point. Since you said there have been adjustments by a new tenant, it's quite possible both of these apply. For example, the system may have had an air pocket that prevented water flow in a part of the system. Bleeding that air would have started heat flowing and causing more thermal expansion. In addition, getting access to the right valves in order to bleed the radiator could have jostled the fin tube from its supports and created some new friction points.

How to fix it: check along the entire loop and eliminate friction points. The most likely friction points and solutions are:

  1. Fin tube supports. The core of the radiator is a copper tube covered in square aluminum fins. The fins are supported from below, usually by a plastic glide -- part #7 in the example below (source: Haydon Corp.), also visible in the first photo as a piece of gray plastic on the bottom of the fins. If the fin tube has slipped off of one of these glides, it may be resting against one of the metal brackets, which could function like a drum during thermal expansion. To fix, remove the front cover of the baseboard and verify that a glide is in place between each vertical support bracket and the finned tube. The front cover is typically snapped onto vertical brackets at the top and bottom and can be removed by hand with gentle prying. (Note: be careful when handling baseboard radiators - they're full of sharp sheet metal! Gloves are recommended.)

    Fin tube radiator labelled

  2. Wall or floor penetrations. The radiator will be supplied by pipes that usually need to go through walls or floors to reach your boiler and continue to service other parts of the building. When a pipe passes through a wall or floor it should be centered within a hole that provides around 1/4" of space around the pipe, so the pipe does not rub against the opening during thermal movement. If you see a pipe resting on an edge of an opening, you can (a) expand the opening or (b) add something soft to cushion the motion and eliminate the noise. Because expanding an opening is often difficult, a good choice for passing is a small section of pipe insulation, stuffed into the penetration around the pipe.

  3. Very long runs. If you have a straight run of, say, 50 feet of finned tubing (perhaps going through some walls, but still pretty straight), the expansion may be significant enough that the plastic glides may not be reliable. In these cases, it's best to add a special expansion coupling to break up the long run. This is the most complex of these typical fixes, because the system will have to be drained, pipes cut, and a new fitting installed (typically soldered).

Most likely, your fix doesn't require opening up walls - just a thorough inspection and a few adjustments, and maybe a few inches of pipe insulation strategically placed. A plumber with experience in hydronic heating system should be able to help with this if needed. Good luck!

  • Thank you so much for the information. There is no noise coming directly from the radiatorThe new occupant is turning radiator on/off around 10:30 am tapping stops - adjusts at 7 pm tapping starts - it started within 2 minutes tonight. Here is a photo of the radiator. photos.google.com/share/… . The manager has serious control issues and disputes any complaint.
    – catnip
    Jan 6, 2017 at 4:08

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