Strange noise behind shower

[KJ24]

There is a strange noises coming from behind the shower in our guest bathroom. The building plumber opened up the wall (photo attached). He believes there is something wrong inside the shower body, that something is “pivoting” inside the shower body when other people on the line use their bathrooms (we are on the 2d floor in a 6 floor coop building). Another plumber came and suggested to install water hammer arrestors on the branches leading to the shower cartridge. A third plumber who didn’t come but heard my explanation on the phone thought one possible reason is that the hot water pipe is expanding/contracting and hits against a stud.

We tested shutting off the entire water supply to the bathroom. This also shut off the water to our private bathroom, which shares the wall opposite where the shower is in the guest bathroom. We hear no noises when the water is shut off. The prior owners renovated both bathrooms about 10 years ago. We moved in last June but didn’t hear any of these noises until November/December. The only things that happened between those dates were (1) the shower cartridge in the guest bathroom shower was replaced, and (2) a different plumber opened up the wall behind the valves to stop a leak.

 

[CENTRALFL]

Is it possible to shut off the water coming out of the heater? At least to see if I can isolate if it's coming from the cold or hot water?

Since.you already have the wall opened up, it wouldn't be much more to put pipe holders to at least eliminate that possibility.

 

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[2stupid2fixit]

I think what I want to know is, how best can you describe the noise you are hearing? Think of something else in your life that you and I have likely heard, and compare it to that. For example, I know what a rattle snake's tail sounds like. I know what a motor that is trying to start but can't sounds like. I know what a celiing fan that has too much dirt on one paddle and spins off balance and makes a whaf-mmm whaf-mmm whaf-mmm sound each time it makes a spin. The noise you are hearing, what does it sound closest to like something else in life?

Plumbing setups can make lots of sounds, but the goal is for plumbing to be silent. If you can upload a good recording as a file, meaning record it from an iphone or something so we can hear it is the absolute best way to approach this because lots of us here know what air entering into a line sounds like and we can likely tell by the sound where it is entering, like bad joint, bad pex crimp, bad pvc glue, bad cartridge, malfunctioning or competing check valves, etc. If you cant upload the actual sound, describe best you can what it sounds like. The plumber that heard your cpmplaint and said it could be the hot water line expanding against a stud: From the very limited info I have, I think this explanation is the closest and best one, because a pvc or pex line (usually not copper tube so much) expands when hot water runs trhough it and heats it up. The photo you provided looks like copper tube to me, but I see lathe in there too, the copper tubing could be running in or laying in notched grooves of studs. If it is loose against wood studs, when the hot water is opened and cool water turns hot, the pipe will actually physically MOVE, and it makes sound, depending on the age of your wood and the acoustics of the enclosure can be anything from a soft to loud DUTT-DUTT-DUTT-DUTT-DUTT until the tubing reaches the maximum that it will, and stops advancing against the wood. If its old wood it could have creosote in it, which can act as an abrasive to the tubing against the wood's surface, and it COULD make sounds much like when you apply the brakes in your car just soft enough to make them "skip". If that's what's happening, The way to cure this is to insulate (foam pipe insulation like pool noodles or loose fiberglass insulation) wherever the tubing is in direct contact with wood. But please try to describe what you are hearing. Even in Florida, the structure can be colder in November, December and cause "friction" between the studs and the plumbing.