What Is the Drain Trap for a Garbage Disposer?

Misconceptions

• A drain trap is not part of the garbage disposal. A drain trap is actually part of the plumbing system that keeps waste moving through your system in one direction only and prevents the backup of sewage gases into your house. All houses with modern plumbing have drain traps. Not all houses have garbage disposals.

Function

• Drain traps are actually part of the drain, waste, vent (DWV) plumbing system of a house. Drains collect water from sinks, showers and baths; waste lines collect from toilets; and vent lines vent sewage gas and help ensure necessary air pressure for the system. The trap part of the drain system is intended to help make sure that odors from the vent lines don't make their way back up the drain lines and into the house.

Types

• There are two different types of drain traps. What type of trap is used is completely dependent upon where in the house the trap is being utilized. If the pipe penetrates into the wall, it will use a P-trap. If the pipe travels beneath the floor, it will use an S-trap.

Significance

• Whichever type of trap you are talking about, its purpose and the effect will be the same. Sewage air will not be able to vent back into your house, and you will not have to deal with any unpleasant smells in your house. This effect is generated thanks to the curvature of the pipe itself. When the pipe is used, water flows through the curved area. When the water pressure is turned off, water remains in the area, acting as a seal to prevent any gas from flowing back through the pipe system. The curve traps water in the pipe and stops any potential air flow---hence the name, "drain trap."

Warning

• Because of the curve of the trap, the trap is the easiest place in a drain system to get clogged. Luckily, in most cases it is easily accessible and easy to remove. Before you unscrew the trap from the rest of the drainage system, make sure you put down towels or preferably a bucket beneath the trap to catch any water that will likely leak from the trap when you remove it.