If your moen bathtub faucet suddenly starts to leak water, or the faucet does not shut off to the end, or the handle does not move easily, there may be a worn or damaged valve cartridge. The valve cartridge controls the hot and cold water outlet of the cock of the bathtub. This can be repaired with a new cartridge by using some basic tools. It is possible to do this by yourself, and that will save you a few dollars.
Cut the water supply to the cock of the bath by turning the water valve to the right. The water valve is usually located near the bathtub or in the basement of the house. Remove the decorative cap on the cock of the bathtub with a flat screwdriver. Remove the single screw on the bottom of the handle of the bathtub faucet with a flat screwdriver and pull the lever away from the key. Loosen the screws of the shield plate with a flat screwdriver, which is located on the wall behind the tap.
Pull the clamp with a pair of needle nose pliers. This is located on the top of the valve cartridge and holds it in place. After removing the retaining clip, grasp the valve cartridge with the needle nose pliers and gently twist it back and forth to release it.