To install bathtub and shower plumbing, expose the studs and piping in the shower walls. Locate the cold and hot water supply lines. Use CPVC pipe or copper tubing to run new water lines, and mount a mixing valve to this. Extend these lines up to where the shower head and bathtub faucet are located. Fit a shower head onto the end of the shower line, and mount a tub spout over the piping.
Shut off the water lines when installing the bathtub and shower plumbing. The water lines, tub spout, shower head and mixing valve must be centered on the shower and tub base in a straight line. Mount the mixing valve over the hot and cold water lines as it regulates and maintains the water temperature to ensure safe showering and bathing.
Set the shower head at the preferred height, and run the water piping or tubing to it. Cut away any excess piping or tubing with a hacksaw or reciprocating saw. When using multiple lengths of piping or tubing, use fittings to connect the pieces together. When the water lines are run, turn the water back on, and check for leaks. If leaks are found, fill them with pipe sealant or caulk.
If a drain must be installed, make sure the shower floor has a slight slope running towards the drain. Install a sanitary tee directly beneath the drain. Use piping or tubing to connect the drain to the sanitary drainage line.