How Does a Sink Drain P-Trap Work?

A sink drain p-trap is an essential part of any household sink. If you've been curious about how these drainage devices operate, read on to learn everything you'll need to know.

Basic Function

Sink drain p-traps essentially enable waste water to safely exit your home's drains and play a vital role in preventing harmful fumes and sewer gases from entering your home through sewer lines. Whenever you use one of your home's drains, waste water is flushed through your p-trap and replaced by fresh water while the trap's water seal keeps the aforementioned fumes and gases from finding their way in. In addition to creating noxious smells, these gases have been known to cause disease and can be highly explosive. All of your home's sinks, tubs, washers and other plumbing fixtures should be equipped with drain p-traps.


Drain p-traps are generally composed of a curved trap piece, a drain elbow and a tailpiece. As previously mentioned, they also feature water seals that prevent sewer gases from creeping up through your drain. Additionally, p-traps are available in both metal and plastic varieties. It may surprise you to learn that metal drain p-traps are more prone to corrosion than their plastic counterparts.