A shower drain is a plumbing fixture positioned between a shower enclosure and a drainage pipe that captures water and funnels it into the sewage waste water system. Unlike a tub drain – where you may find a shower installation also – a shower drain does not normally incorporate a levered fixture which blocks the drain in order to allow water to fill the tub.
Every shower drain includes a grid, strainer, vent and trap. The grid has an arrangement of holes or slots that allow water to freely flow through them. The strainer is immediately below the grid and prevents objects large enough to clog the drain or waste pipe from entering the drain. The trap is a u-shaped pipe that traps water in order to block sewer gasses from escaping back up the drain into the bathroom. The vent is a pipe that provides air pressure in the system.
The challenge for shower drains, and all fixture-to-waste junctions, is to perform the task of moving water from one to the other without leaking and without allowing gasses from the waste system to backup into the house. This is accomplished by choosing the correct shower drain for the existing type of shower and drainage pipes, and by installing the drain system correctly.
Choosing the best shower drain. When selecting a drain, it is important to consider the type of waste pipes to which the drain will be connecting. Non-metal tubing such as plastic can use threaded, compression, crimped or solvent-welded drains. Threaded drains screw into the shower and piping using a special plumbing tape wrapped around the threads that creates a waterproof seal. Compression and crimped drains use pressure to force a tight connection. A shower drain that is solvent-welded uses a solvent compound that causes a chemical reaction that bonds the drain to the pipe. Metal pipes require drains that are either threaded or welded with a soldering metal.
Installing traps and vents. Once the correct type of drain is selected, it is then important to make sure it is installed correctly. First, a trap should be installed directly below the drain. This is a u-shaped bend in the pipe that traps water in the pipe. This trapped water acts as a block and prevents sewer gasses from escaping back up the drain into the house. Next, it is necessary to install a vent pipe above the level of the drain. The vent provides an air supply that keeps the water in the trap from being sucked out of the trap, either up into the shower or down into the waste system, by ambient air pressure.
When the appropriate drain is installed correctly, the new shower drain will handle water flow without leaking and without allowing noxious smells to enter the house.