What Does a P Trap Do in a Plumbing System?

What does a P trap do? It serves a myriad of functions that keep your plumbing system healthy. 

Whether you have unanswered plumbing questions or need your P trap unclogged, our World Class Services team can help. For every plumbing issue, we’re Westerville’s trusted plumbing company. Call us at 614-587-8985 to book an appointment today.

What Is a P Trap?

The P trap is the curved portion of pipe underneath the sink or shower in your kitchen and bathroom. It captures any waste from the sink, preventing it from clogging the rest of your plumbing system. It also prevents toxic sewer exhaust from seeping back into your house.

The P trap uses water to create a seal that works with the drain trap, near the drain pipe. This allows water to flow through but prevents it from coming back into your system. The bottom of the pipe contains a small tap used to clean out cogs.

The three most common materials for a P trap include:

  • Brass is appealing to the eye but corrodes over time. It’s used mostly for exposed pipes because it looks better than the PVC option.
  • Steel, like brass, provides a significant boost of style over the PVC option. However, it’s vulnerable to corrosion and needs eventual replacement.
  • PVC and plastic-based pipes resist corrosion and acid but don’t offer the stylistic benefits of metal-based pipes. Their light weight means they’re easy to assemble and disassemble.

Common P Trap Problems

While relatively durable because of their design, P traps are susceptible to two primary problems.


P traps handle most forms of waste without issue. However, objects such as wet wipes, paper towels, and large quantities of hair can cause severe clogs in the trap. Never put waste in your sink that doesn’t belong there.

Over time, even common substances like soap scum and grease can build up in your pipe and make clogs more frequent.


Your P trap depends on keeping a layer of water at the bottom to maintain a seal and trap exhaust. When the P trap dries up, exhaust and wastewater can back up into your sink or shower. Other than evaporation, a leak, clog, or dry air also dries a P trap.

How to Install a P Trap

Now that you know the answer to “What does a p trap do?” are you tempted to install your own? While installing a P trap is much easier than other plumbing jobs, hiring a professional plumber prevents improper installation or other mistakes that lead to serious problems.

If you’re attempting a complicated bathroom or kitchen layout, know you can’t connect more than three sinks to a single P trap. If you live in a dry climate or don’t use your sink often, ask the plumber to install a trap primer to prevent evaporation.


Your plumber will measure the pipe so it fits snuggly into the wall. They’ll connect the P trap to the pipe in the wall and verify an airtight seal. 


Showers are more difficult to install as they usually connect directly near the drain. Your plumber follows the same procedure as the sink installation: cutting, fitting, and testing the seal.

Maintaining Your P Trap

While P traps don’t require much maintenance, keep the following tips in mind to prevent clogs and evaporation.

Avoid Foreign Materials

Never put anything down your sink that doesn’t belong. Minimize food waste by dumping as much as possible into the trash. Don’t drain grease or fat directly into the sink.

Gum, paper towels, and animal bones all clog your P trap, requiring professional maintenance.

Hydrate Your Pipe

To keep your P trap from drying out, dump a gallon of water down your sink every three months. The water replenishes any evaporated water and keeps out disgusting sewer gas. Your plumbing pipes are most vulnerable during the winter months, so focus on hydrating them during the cold season.

Regular Cleaning

If you notice your P trap clogs frequently, you might need annual cleanings. You might feel as though you did something, but don’t feel bad: soap scum, cold weather, and hard water all cause problems with clogging.

Call World Class Services for All Your Plumbing Needs

Now that you know, “What does a p trap do?” you’ll know when it needs maintenance. Whether you’re wondering how to avoid damage to the plumbing system or need your pP trap replaced, our team at World Class Services is here to help. When you need an appointment, call us at 614-587-8985.

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