What’s a P-Trap and What’s it For?

what's a p-trap?

Even if you don’t know what a “p-trap” is, we guarantee you’ve seen them before. A p-trap is the curved, p-shaped series of pipes under the sinks in your bathroom and kitchen. You’d never know it just to look at them, but p-traps are a very important part of your home’s plumbing.

Knowing what p-traps are and what they do is important info for anyone who wants to keep their plumbing working effectively for as long as possible. Here’s everything you should know about one of the most important parts of your plumbing system.

What exactly is a p-trap?

P-traps get their name because of their distinct shape. They consist of two 90 degree joints affixed to a horizontal overflow pipe, creating the telltale “p-shaped” curve. One of the joints exits the sink drain and attaches to the next pipe. That pipe contains a water seal system, which allows water to move into the overflow pipe without backing up. P-pipes are usually made of either steel or PVC. They serve several important purposes for your plumbing fixtures.

What does it do?

The main purpose of the p-trap is to keep potentially damaging sewer gases from finding their way into your home. The gases they “trap” include methane, hydrogen sulfide, nitrogen oxide, sulfur dioxide, and ammonia. These gases can cause horrible, lastling smells and even health problems like headaches, fatigue, lightheadedness, and pneumonia.

P-traps also rap debris that might otherwise cause clogs further down your plumbing system. They’ll catch food waste, hair, and other things. The p-trap’s shape and location makes it much easier to clean out than other pipes. Finally, p-traps also catch small items that you may have accidentally dropped down the drain. If you accidentally drop your wedding ring down the sink, for instance, the p-trap can keep it from flowing to the sewer. P-traps have probably saved some marriages!

Are there common p-trap problems I should be aware of?

P-trap can get overloaded if too many appliances are connected to a single trap. Typically, you should only connect a maximum of two appliances to any p-trap. If a p-trap connects to a plumbing system without ventilation, it could be slow to empty. P-traps that contain too much residual water make a “glugging” sound when water runs through them. When p-traps gurgle, they’re not working as effectively as they should be. In some cases, they could even be releasing some of the sewer gas they’re supposed to contain.


If you have any more questions about p-traps, or how you can better take care of your home’s plumbing, get in touch with the team at
Ben Franklin Plumbing today.