Faucets make many different types of noises from common water hammer to high-pitched squealing sounds. If your faucet squeals or hisses, it probably isn’t a pressure problem but a loose washer.
Most faucet squealing noises come from a loose washer inside the handle of the faucet. The washer sits at the base of the handle, underneath the stem, and it allows the handle to turn without grinding against the backside of the faucet seat. In many faucets, this part is called the seat washer.
When this washer is loose and water flows past it, the washer flaps or vibrates causing a hissing, squealing or screeching sound in the faucet. Fixing this noise is not a big deal, it just requires just a few very basic plumbing skills.
First, turn off the water to the faucet and take off the handle by unscrewing that small screw at the base of the handle with an allen wrench and pulling it off the faucet. Unscrew the stem or take out the cartridge, and find the washer at the base of the handle. Remove the washer and replace with an exact replacement part for your particular model faucet. Tighten everything up again and turn on the water.
If the noise is still there, replace the washer on the other side, or inspect the cartridge for debris. Sometimes debris lodged inside the pipes will cause a squealing noise in your faucet.