What’s the Purpose of a P-Trap?

Water from the faucet does not make a straight line to the drain. There’s a U-shaped bend in the pipe directly beneath the sink drain through which wastewater travels before it goes down the drain. That’s the P-trap and it plays an important role in how your plumbing functions.

Bathtubs and showers have P-traps, too, and toilets have an internal S-trap which performs a similar function.

A P-trap Prevents Odors

The curve in P-Trap always retains water. Water is trapped at the bottom of the curve -- hence the name. This small volume of water prevents sewer gases from entering your bathroom, sparing your nose from nasty odors and protecting your health. Every time you use the sink, running water flushes out the old water and replacing it with new.

If You Smell an Odor…

As long as water remains in the P-trap, stinky sewer smells can’t rise up through the drain. If your home smells foul, shine a flashlight into the sink drain. If you don’t see any water, run the tap.

There are only two reasons why the P-trap would be empty: Water inside evaporated from disuse or there’s a leak. Check beneath the sink for excess moisture.

A P-trap Catches Solids

A P-trap prevents solids from entering your drain -- a say, a child’s toy. If you accidentally drop your wedding ring down the sink, you can easily retrieve it by disassembling the P-trap. Here’s how.

  • Place a bucket under the P-trap
  • Use a pair of water pump pliers to remove the lock nuts
  • Slide the P-trap out and empty the contents

There, you just got your ring back!

Before re-assembling the P-trap, take a moment to clean it. Run a pipe brush through it to remove gunky build-up, then take it to another sink to rinse thoroughly. Also, check the washers on the P-trap. If they’re hard and cracked, replace them.

Bottom line: Complications with the P-trap -- either odors or dropped objects -- can be easily solved with water or a pair of pliers and a pipe brush. If you need expert help, turn to the pros at Integrated Plumbing Solutions. Call (770) 343-7370 to schedule your appointment.