We have one faucet that emits a horrible, high pitched, squealing noise. When it does this, the water at the faucet is off and there are no drips (sink is completely dry; no drips in an hour+).
Tends to happen in late afternoon and throughout the night.
If the faucet is left to drip at the slowest possible rate, the squealing noise stops entirely.
My uneducated guess is that air is building up at the faucet and water pressure is driving the air out of the faucet, which happens to squeal when it does so. Since it seems to happen when the air temperature — and pipe temperature (over the roof piping that is insulated, but still gets cold overnight) — drops, I'm not sure why that would cause it to be worse and not improve.
Unless it is sucking air in through the faucet?!
Best Answer
It's a type of water hammer enabled by an incomplete seal, tighten it further if that silences it you need to repair the valve, a new washer might do it, or the valve seat may also need fixing.
Overtigtening causes accelerated wear on the valve stem thread, and so should not be treated as a fix.