I recently utilized the governments shower head swap scheme and swapped over our shower head with a new water saving head and ever since, we have had a high pitch squeal (it is deafening) coming from it. It comes and gos when the taps are adjusted (It squeals mostly when the taps are down low but it doesn’t seem to do it when the taps are turned up fully). I have also tried turning down the isolation tap near the meter to reduce pressure (which worked a little bit) but it still produces this squeal. We also recently changed the washers in the taps as well (before the shower head was replaced) so I know these are brand new. Please help!
In this situation, as you have already tried most of the things, I would recommend you to take professional plumbers help to fix this high pitched squeal in your shower.
Generally the noise you describe is related to some type of obstruction in a valve, pipe, or fixture, or a loose component. You probably need to remove the shower head and soak the end of it in “Lime-Away” to remove the built up lime from the jets.