Fixing a shower faucet leak usually involves replacing a worn O-ring. The O-ring is a small rubber ring which seals the different parts of a shower together at the joints. You may have an O-ring that slips into your blender or food processor. Your local hardware store will have a number of O-rings in different sizes. Most showers are uniform. It is a good idea to remove the old O-ring first. Then, take it to the hardware store to find the right replacement.
A Simple Repair
Remove the worn O-ring in 3 simple steps. First, remove the handle and escutcheon to expose the shower valve. The escutcheon is the plate behind the handle. There is one valve in the center, the control valve. There is a valve on either side of the control valve for hot and cold water. Second, shut both of these off with a screwdriver. You should not be able to remove the control valve cartridge. Take this part to the hardware store, and fit it for a replacement O-ring. Fixing a shower faucet may involve replacing the cartridge in some rare cases.