Repair a leaking Delta shower valve by replacing the cartridge. Prior to starting the repairs, shut off the water supply at the main. Most repairs can be done without cutting through the drywall behind the valve.
Protect the tub by placing an old towel over the drain. This also prevents any small pieces from falling down the drain. Remove the decorative cap from the valve handle and the screw that holds the handle on the stem. Pull the handle from the stem, and loosen the screws that hold the trim in place. Remove the plate to expose the valve, and slide off the outside sleeve. Use water pump pliers to remove the brass bonnet nut from the assembly.
Remove the plastic plate from the valve, and pull the cartridge out of the assembly, using a slight wiggling motion, if necessary. Delta uses several different styles of assemblies, so take the old one to the home improvement or plumbing store to ensure purchase of the correct replacement.
Clean the inside of the valve, removing all debris. Push the new valve in place with the side marked Hot to the left. Once it is firmly in place, install the new limit stop by following the manufacturer’s directions. Replace the bonnet nut, and turn it until snug using the pliers. Reassemble the valve, and turn on the water.