P-Trap Clogged: 3 Common Reasons & Fixes (Do This!)


P-traps – the U-shaped pipes under sinks – are essential plumbing elements designed to keep sewer gases out of your house. Due to the trap’s shape and the material it is made of, a P-trap rarely gets clogged.

However, if you notice slow drainage, a clogged P-trap can be the culprit. 

Hair and soap scum build-up are the most common reasons for a clogged P-trap. Oil and grease congealed on the pipe are other frequent issues in kitchen sinks. A mixture of baking soda and white vinegar might be able to wash the clog down the drain. If it doesn’t: 

  • Turn off the water to the fixture.
  • Place a bucket under the trap and unfasten it from the sink’s tailpiece and wall fitting.
  • Let the trap soak into a bucket filled with a mixture of white vinegar and baking soda. 
  • Remove the clog and clean the trap. 
  • Reinstall the trap, turn on the water and let it run for a while to check for leaks.

Why Is My P-Trap Clogged?

Fixture traps are crucial components of a drain system designed to block sewer gases out of the home. All building and plumbing codes require them, but for them to work properly, they must be free of gunk and clogs. 

Because of their essential role, brands improved their manufacturing techniques over time. Today’s P-traps are generally made of PVC and have very smooth insides that don’t allow gunk to grip onto the surface. 

However, there are a few common things people wash down the drain that can lead to recurrent clogging: hair, oils and grease, and rogue objects. 

Hair 

The most common cause of a clogged P-trap in the bathroom is hair washed down the drain.

Hair strands can easily mix with soap suds as you’re using the sink, and soap generally grips onto the hair. This leads to a mixture of hair and soap scum that can stick to the pipe’s walls. 

Soap scum often hardens on the surface, and together with the hair, it can cause recurrent blockages. 

Oil And Grease

If hair is the most common cause of a clogged P-trap in the bathroom, oils and grease washed down the drain are the most common causes of clogs in kitchen sinks. 

Many people dispose of cooking oils and grease down the kitchen sink drain because they are liquid when thrown away.

However, not many people know that both oil and grease can congeal on the pipes quite easily, especially if you’re using cold or lukewarm water. 

Hardened grease can build up on the pipes, reducing their diameter. This could make it hard for other debris – such as food bits – to pass through.

For this reason, it is crucial to clean the trap with a degreaser before putting it back on. Otherwise, you may not get rid of the grease build-up, and the problem will keep occurring over and over again.

Rogue Objects 

Another thing that can lead to a clogged P-trap is a rogue object accidentally washed down the drain. This could be a small toy, chunkier piece of jewelry, and even socks or underwear. 

Because of the nature of the clog, homemade solutions and chemical plungers are unlikely to work. You’ll have to take the drain apart and remove the offending object. 

How To Unclog A P-Trap

No matter what clogged your P-trap, unclogging and cleaning it is a beginner-level task. Follow the steps below to get rid of the blockage. 

1. Gather The Necessary Supplies

To clean and unclog the P-trap, you’ll need: 

  • Baking soda
  • White vinegar 
  • Bucket 
  • Pliers or adjustable wrench 
  • Wire coat hanger 
  • Bottlebrush 
  • Rag 
  • New P-trap (optional)

2. Wash The Clog Down The Drain 

Before removing the P-trap from the drain, you can try to wash the clog down and see if it solves the problem. 

To do this, pour half a cup to a cup of baking soda down the drain and leave it for five to ten minutes. 

Pour a cup of white vinegar into the drain. When vinegar and baking soda mix, they generate a fizzy reaction that can break down gunk and grease. Wait for ten to 15 minutes. 

Turn on the hot water at another faucet in your home and let it reach the highest temperature. Alternatively, heat the water on the stove, but make sure it doesn’t reach boiling temperature – water that is too hot can damage the PVC pipes.

Fill a bucket with hot water and pour it down the drain.  

Put on the stopper and fill the sink with water. Remove the stopper and see if it drains properly or if there are still issues.

3. Remove The P-Trap 

If the baking soda and white vinegar method didn’t work, it’s time to remove the trap and clean it properly. 

To do this, turn off the water to the fixture first. While you can remove the trap without turning off the water, you risk getting soaked while working if someone accidentally turns on the faucet. 

Place a bucket under the trap. 

Try to unfasten the coupling nut connecting the trap to the tailpiece. If you can’t turn it by hand, use a pair of pliers or a wrench to force it loose. Unfasten it completely and let the trap rest in the bucket. 

Unfasten the nut connecting the trap to the wall fitting and remove it from under the sink. Push the end of a rag into the wall stub to block sewer gases.

4. Clean The Trap 

Pour half a cup of baking soda directly into the trap. Let it sit for a few minutes, then pour a cup of white vinegar (the trap should still be into the bucket).

Wait until the bubbling stops and fill the bucket with hot water. Let the trap soak for a few hours or, preferably, overnight. 

Throw the water from the bucket down the drain and refill with clean water. Use a wire coat hanger to remove the clog and a bottlebrush to scrub clean the trap’s interior. 

While the vinegar generally dissolves soap scum and grease, you might want to use a degreaser if the trap is particularly dirty. Rinse the trap thoroughly when you’re done and let it dry. 

5. Reinstall The Trap

Reinstall the trap by connecting it to the tailpiece first and then to the wall fitting. If you’ve damaged the coupling nuts when unfastening them, replace them with new ones or install a new trap. 

Turn each nut by hand until it feels firm in place. Turn on the water and let it run for a few minutes. Check for leaks before declaring the task completed.

Conclusion 

Washing hair and grease down the sink drain can result in a clogged P-trap. Luckily, cleaning it is easy. However, if the steps above didn’t work, you’re most likely dealing with a sink clogged past the P-trap. You might want to call in a plumber to fix the issue.

Learn More About Sink Traps Through These Articles:

  1. P-Trap Smells
  2. How To Connect P-Trap To Wall Drain
  3. Does Garbage Disposal Need P-Trap?
  4. How To Fix Kitchen Sink Clogged Past Trap
  5. J-Trap Vs. P-Trap

Roxana Bikfalvi

Roxana is a copywriter passionate about home improvement and interior design. When she’s not writing, you can find her upcycling old furniture or remodeling interiors. She has written for numerous home improvement blogs before joining PlumbJoe.

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