Installing separate 3/4-inch lines to supply the shower ensures good water pressure and protects from temperature changes when another faucet is turned on or the toilet tank refills. Tap into the cold and hot water lines as close to the water heater as possible.
Choose the tub or shower faucet before you run pipes. Follow the manufacturer's directions for plumbing the faucet. If your faucet does not have integrated shutoff valves, install shutoff valves in the lines to the valve.
Assuming an 18-inch-tall tub, position the faucet about 28 inches above the floor for a tub, about 48 inches for a shower. You may want to compromise and position it about 38 inches above the floor.
About half a day to run supply lines and install a tub/shower faucet
Drill, tubing cutter, multiuse wire brush, flame guard, propane torch, damp rag, groove-joint pliers
Accurate measuring and drilling, working with copper pipe
Tap into the hot and cold water lines and run 3/4-inch pipe up into the room; if needed, move a stud to make room for the plumbing behind the tub
Tub/shower faucet, copper pipe and fittings, flux, solder, pipe-thread tape
Most faucets come with a plastic cover that protects the faucet and serves as a guide for the depth at which it must be set. To determine where to place the braces, consider the total thickness of the finished wall -- often 1/2-inch-thick backerboard plus 1/4-inch-thick tiles.
Assemble all the pipes in a dry run. Install 3/4-inch pipe up to the height of the faucet, add reducer couplings or elbows, and run short lengths of 1/2-inch pipe to the threaded adapters on the faucet. Add hammer arresters. Anchor the faucet according to manufacturer's directions.