What is a P-Trap? How does it work and how can you clean it? (2024)

Posted by Swan Heating

What is a p-trap, how does it work and why is it important?

If you’ve ever encountered problems with your sink’s drain, you’ve probably heard the term p-trap thrown around here and there. While it is a simple device, few homeowners understand how it works and why it matters. Here’s a quick overview of p-traps you can reference when sink-related plumbing issues arise in your home.

What Is a P-Trap

In a nutshell, a p-trap is a u-shaped bend in the waste pipe that connects a sink’s drain to a home septic tank or to a municipal sewer system. Under normal circ*mstances, p-traps always contain some water.

What is a P-Trap Used For

The most critical task of the p-trap is to prevent noxious gases such as methane from making their way into a home. These traps also allow homeowners to quickly and easily recover small items that fall down the drain. Long story short, they’re an integral part of modern plumbing design.

Problems You’re Likely to Encounter

By far the most common issue associated with P-traps is the accumulation of debris in the bend. Over time, things like hair, food, grease and mineral deposits build up and reduce the diameter of the drain pipe. Eventually, the drain will clog up and have to be thoroughly cleaned out.

Another potential problem with P-traps is that they can eventually vent sewer gases into a living area. This usually occurs because the water in the trap evaporates over the course of several weeks and isn’t around to capture expanding gases. Fortunately, this problem can be easily remedied by periodically running water through drains that are seldom used.

P-Trap Cleanout

If you have a sink that’s draining slowly, the simplest way to deal with the problem is by running a drain cleaner through the pipes. Drain cleaners attack and destroy grease or mineral deposits on the walls of a pipe to increase water flow through the P-trap assembly.

Another great way to deal with a fully or partially clogged drain is running a “snake” through the conduit to dislodge obstructions. Snakes are simply flexible cables that are inserted into drains for the purposes of scraping pipe walls. Good snakes have a handle on them that allow users to rotate the cable to grind off deposits.

If a chemical cleaner or a snake won’t clear a clogged pipe, physically removing the p-trap and cleaning it by hand is the only solution. Once removed, p-traps should be scoured thoroughly to ensure that waste water flows through efficiently. Care must be taken when reinstalling the trap to guarantee that no seals or PVC welds leak.

What to Do When Problems Arise

When drainage issues plague a sink in your home, it’s likely that a P-trap problem is to blame. Bringing in an a local Denver plumber to assess and rectify the situation is highly recommended. Doing so will save you time and money when all is said and done.

Have more plumbing questions? Read about bathroom drain smells, HET toilets or check out our home plumbing tips.

What is a P-Trap? How does it work and how can you clean it? (2024)

FAQs

What is a P-Trap? How does it work and how can you clean it? ›

This pipe is U-shaped, and it helps to collect and drain water. This helps to prevent odors and gasses from coming back up the pipes and into your home. Over time, your P-Trap can start to smell due to build-up and you will need to clean it. Cleaning this pipe will help you to avoid costly repairs in the future.

How do you clean the P-trap? ›

Simply dump the water in the pipe. Then manually pull out anything that may be sticking out of the P-trap. Next, wet your flexible wire brush and push it through the trap. Periodically rinse the brush and keep cleaning the trap until you're not seeing any residue on the brush.

What is a P-trap and how does it work? ›

P-traps, named after their shape, contain a u-shaped bend that filters wastewater as it enters a plumbing system. The trap is connected to a sink, bathtub, and shower with a J-bend on one end and exits into your drainage system. The J-bend is the section of the p-trap that resembles the letter J.

How do you tell if a P-trap is clogged? ›

A blocked p-trap will cause water backflow to occur. The first sign that your p-trap is clogged is when the water in your sink takes longer than average to flow down the sink.

How do you clear a clog past the P-trap? ›

Kitchen Sink Clogged Past P Trap: How to Fix
  1. Step 1: Baking Soda and White Vinegar. These common pantry items double as superstars of the DIY world. ...
  2. Step 2: Follow Up with Hot Water. Next, run hot (not boiling) water and see if you've conquered that clog. ...
  3. Step 3: Plunge the Sink. ...
  4. Step 4: Unscrew and Clean the Sink's P-Trap.
Nov 2, 2021

How often should I clean my P-trap? ›

You should clean your P-Trap every one to three months. This will help to ensure that you do not smell any sewer smells in your home. It will also help to ensure that your drainage system runs as it should.

Do p-traps get clogged? ›

Unfortunately, the trap's water-trapping ability extends to hair, grease, debris, and soap scum. This makes a P-trap the number-one location of clogs in the sewer system. If the P-trap becomes only slightly clogged, then you experience slow drainage in the fixture.

Do I need to turn off water before removing a P-trap? ›

Turn off the water supply to the sink that you're working on from either your PEX manifold, or by turning the supply valve for the entire house off. This isn't a necessary step, it's more about preventing you from flooding your kitchen by running the water while the p-trap is removed and cleaned.

What happens when P-trap is clogged? ›

If this happens, the P-traps under your sink may become dry, and the sewer gas may accumulate. You hear a gurgling noise from the sink or tub. The water in your toilet seems weak, and the bowl isn't refilling quickly enough after a flush.

What does a P-trap drain look like? ›

If you take a look inside the cabinet under your kitchen sink, you should see a piece of PVC pipe with a U-shaped bend at the bottom. This is the P-trap, which gets its name from the fact that it somewhat resembles the letter P flipped on its side. The trap has threaded fittings on both ends.

What does a bad P-trap smell like? ›

A regular sewer-gas smell is just a bad stink with a definite odor of feces and sometimes a rotten-egg (hydrogen sulfide) smell and/or a moldy mustiness too.

Can a drain snake go through a P-trap? ›

It's typically a good rule of thumb to remove this P-trap before you insert the plumbing snake to make it easier to get into your drain pipe. If you were to leave the P-trap in place, you would have to remove the inside of the drain and try to go around the P-trap curve.

How do you clear a P-trap but the sink won't drain? ›

If the bathroom sink is not draining even though the pipes and P-trap are clean, there are a few other possible causes that you can investigate: Check the stopper: The stopper may be obstructing the drain, even if the pipes and P-trap are clear.

What is the black gunk in my P-trap? ›

The "creepy black stuff" in your drain is made up of a combination of things, mostly decomposing hair, soap scum, toothpaste grit, shaving cream residue, skin cells, etc.

Does Drano go past the trap? ›

Also, the trap configuration in toilets prevents these products from reaching areas where matter can accumulate and cause plumbing problems – so these products are ineffective in toilets.

What is the black stuff in my P-trap? ›

The black gunk that accumulates in your drain is created by a build up of bacteria living on hair, hand soaps, shaving cream, skin cells, lotion, toothpaste, and phlegm.

Should there always be water in the P-trap? ›

Running your sink obviously flushes water through the trap and down into the drain line. However, when you shut the faucet off, a small amount of water always remains inside the bend at the bottom of the P-trap. This water acts as a barrier that seals off the pipe so that the smelly sewer gases can't escape.

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