What Is a P-Trap?

A p-trap is an essential part of virtually any drainage system. Here are the the basics of p-traps in terms of their appearance and function.


A typical p-trap is made up of a curved trap piece, a drain elbow and a tailpiece. In addition, p-traps feature a water seal that allows waste water to flow safely into sewage systems while preventing dangerous fumes and gases from entering you home through sewer lines. P-traps come in both plastic and metal varieties. Surprisingly, metal p-traps have a tendency to corrode at a much faster rate than their plastic counterparts. Also, p-traps vary in size from 1.25 inches and 1.5 inches in diameter.


The basic function of a p-trap is to ensure that waste water is properly drained and fresh water is able to take its place. Each time one of your home's drains is used, the waste water is flushed through the drain's p-trap and subsequently replaced by new water without any harmful gases or fumes finding their way into your drain. P-traps are used for tubs, washing machines, sinks and most other common household plumbing fixtures. P-traps will inevitably wear down and incur clogs over time, but fortunately, they are relatively easy to replace.