How to Know What Kind of Shower Valve to Use

Count the number of handles on the shower. If you have one, you will need a ball valve, cartridge or ceramic disc. For two handles, you will need either a washer-based valve or a ceramic-disc valve. Three-handled showers use a diverter in the center handle and the same type of valves under the water taps.
Insert the tip of a thin blade into the top of the flat cover plate on the handle to remove the cap.

Remove the screw under the valve cap and pull off the handle.

Pull the cover plate at the base of the handle off to access the wall.

Remove each of the parts of the shower valve in reverse order, and examine them to determine the type of valve you need.

Look for a washer on a two-handled shower, which indicates you need a compression valve. Washers are small, flat metal discs that press against the valve to create a seal in a compression valve. If you find a washer, replace your current valve with another compression valve.

Examine the parts removed from your shower. If you determined it doesn't have a washer, look for a U-shaped locking clip. This clip holds in the cartridge for a cartridge valve. A ball-shaped assembly on a single-handled shower means you need a ball valve. If you find three small ceramic discs under the handle in a one- or two-handled shower, you need a ceramic-disc valve.