P Trap

What is a P Trap

Definition of P Trap in Construction

The term P trap is the popular term used to describe almost all residential and many commercial plumbing traps. The reason for the term is that the actual plumbing layout of a P trap resembles a P lying on its side. A P trap is a piping arrangement that traps a quantity of fluid in the elbow of the P. This fluid provides a seal to stop any sewer gas from exiting from the piping system. In the majority of situations, the fluid in the elbow of the P trap will remain in place, until the system is used again. There are occasions when the systems are not used quickly enough to allow the trap to refill, and evaporation has depleted the trapped fluid. If this occurs, the sewer gas will be able to flow out of the outlet of the piping system and cause health issues as well as a very unpleasant odor. The simple solution to this problem is simply opening the water faucet on a periodic schedule to fill the trap, prior to all of the fluid evaporating. In commercial, industrial and manufacturing facilities the use of a primer to keep the P trap filled with fluid is sometimes utilized. The use of this primer arrangement is very rare in residential construction.