Most local plumbing codes need pressure-regulating shower valves as an issue of safety, and if you don’t have one on your bathtub, you might have found the reason for this by experience. Without this type of valve, your bathtub water may suddenly turn scaldingly hot when someone else at the home turns on a tap or flushes the toilet, and you can find a minor burn or slip when seeking to escape the way. You can not turn your existing shower valve into a pressure-regulating one by changing a cartridge; you have to set up a new valve.
Removing the Old Valve
Turn off the water into the bathtub, either by finding and shut the valve which controls the toilet or turning the water off for the whole house. Open the bathtub faucet and let water drain.
Remove all of the shower trim. Unscrew the bathtub arm by turning it counterclockwise with a pair of adjustable pliers. Remove the handle using a screwdriver and pry the trim plate off the wall using a flat-head screwdriver. You don’t have to eliminate the inner valve mechanism.
Find the access panel to the shower plumbing. If it is not behind the bathtub or in a cupboard beside the bathtub, it might be in a closet in an adjacent bedroom. If you can not locate a panel, cut a hole in the wall behind or next to your shower valve approximately 24 inches high, in the height of the tub manage, and involving the flanking studs, then using a drywall saw and reciprocating saw.
Cut all of the pipes attached to the old shower valve using a pipe cutter. Make the cuts several inches away from the valve to give yourself room to set up fittings for the new valve. Pull the old valve along with the pipe which connects the valve into your shower head.
Installing the New Valve
Ready the valve by installing any adapters needed to link it to the plumbing. For example, if the valve has threaded female pipe inlets, screw a threaded man sweat adapter to each inlet. Wrap plumbing tape around the threads of the male matching before tightening it into place using a wrench.
Remove the handle, valve caps and internal valve mechanism in the valve body. These parts usually contain plastic parts that could get damaged from the heat produced while soldering.
Secure the valve body into the framing so that the entrance is flush with the bathtub wall. You might need to install new framing blocks to perform this. Use 2-by-4-inch lumber or 1/2-inch plywood for the blocks, and fasten them into the existing framing using screws. Screw the valve into the the framing.
Combine the water lines into the valve using appropriate pipe and fittings. Depending on the positioning of the inlets on the valve, then you may or may not have to install elbows. Dry-fit all of the connections, then disassemble each one in turn, spread flux on both the pipe and the matching and solder the joint using a torch and lead-free solder.
Install the pipe for the new shower head and then shake that pipe using a drop ear elbow twisted into the framing. Finish up by installing the shower arm, shower head and valve manage.