The most prominent piece of a shower's plumbing system is the showerhead. This is simply an outlet for water, and is generally placed about 6 feet or slightly higher from the shower floor. Many showerheads are available on the market, and some come with additional features such as detachable heads, massage wands and individual flow controls. Water is supplied to the showerhead from the mixed side of the shower's mixing valve, meaning that all water supplied to the showerhead comes after the temperature mixing process and flows through the showerhead without additional mixing or modification.
The drain is an overlooked and underappreciated component of a shower, as long as it functions properly. Its purpose is to direct the wastewater out of the shower and to the main waste line of the home. This is done by using a trap configuration, just like a toilet or sink drain, in which water caught in the bottom of a pipe trap forms an airtight seal between the top of the drain, which is exposed to the shower, and the actual waste line. This prevents gases and odors from escaping back into the shower. When water flows into the drain, it comes in on the high side and forces water out of the trap on the low side, which is the side connected to the waste line. This force, combined with a gentle slope of the waste line, causes the water to run freely through the drain, through the trap and down the waste line.
The mixing valve is really the core of a shower's plumbing system. The exact configuration depends on the manufacturer, but these valves are generally configured with either one handle spinning in a clockwise direction to control the amount of hot and cold water allowed into the feed to the showerhead or with two handles -- one for hot and one for cold -- to control the flow of water.
In either configuration, the valve itself is made up of two loops of copper pipe, with two feeds in and one feed out. Hot and cold each come in to the valve separately where the handle or handles on the valve control how much each individual valve allows through. When both the hot and the cold valves are open, the two temperatures of water mix and are fed through the single outlet from the mixing valve. This outlet connects to a pipe that feeds the showerhead, thereby supplying the mixed water to the showerhead and into the shower.
Putting the Pieces Together
Shower plumbing is often sold in kits, which includes the mixing valve and the finished components of the shower, including the showerhead, faucet or valve handles and a drain. These kits almost always require the installation of a copper pipe linking the pieces, such as the feed from the mixing valve to the showerhead.