Shower mixing valves have two primary functions: monitoring the water temperature and mixing hot and cold water to the proper temperature for one-handle shower fixtures. Occasionally, mixing valves may wear out or break and the water temperature cannot be adequately adjusted. It is possible to remove the mixer on a shower with a few basic tools rather than hiring a professional plumber for the job.
Flip the circuit breaker to off for the bathroom and shut off the water to the shower. The shutoff valves are usually in an adjacent room or in the basement near the water heater. Lift up the faucet handle in the shower to drain the remaining water in the line and relieve the pressure.
Remove the screws that secure the faucet handle in place with a screwdriver. Loosen the screws that attach the trim plate with a screwdriver. Pop off the cover plate with a flathead screwdriver to reveal the mixing valve beneath it. Loosen any screws holding the valve in place.
Loosen the valve with two pipe wrenches and place one on the plastic ring connected to the valve and the other on the pipe. Twist the pipe wrenches in opposite directions and the wrench placed on the valve should turn in a counterclockwise direction.
Take off the bolts attaching the valve with the appropriate-size socket wrench and turn in a counterclockwise direction.
Twist the pipe wrench on the valve in a counterclockwise direction. Once the valve is completely loosened, pull it off.