In this video, Ask This Old House plumbing and heating expert Richard Trethewey helps a homeowner silence a shrieking shower.
1. Turn off the water to the shower at the water main or well pump.
2. Pry off the index from the shower handle with a pocketknife or narrow-blade screwdriver.
3. Unscrew and remove the handle from the shower valve.
4. Use pliers to loosen the retaining nut that secures the mixing-valve cartridge.
5. Pull the cartridge straight out of the valve.
6. Remove the old rubber seats and metal springs from the valve.
7. Install new rubber seats and springs using a Phillips-head screwdriver to guide them into the openings in the valve.
8. Press a new mixing-valve cartridge into the valve, then thread on the retaining nut and tighten with pliers.
9. Push the old handle onto the new cartridge.
10. Turn on the water and test the shower.
11. Remove the handle and use a hex-key wrench to adjust the safety limit on the valve to prevent scalding.
12. If the squealing sound returns, clean or replace the showerhead or tub spout with diverter.