What Is a P-Trap?

Almost any household plumbing feature that drains water has a p-trap. Sinks, showers and washing machines all have p-traps to drain the waste water. While it is a simple device, few homeowners understand how it works and why it matters.
California codes require a p-trap any place there is an open drain line that flows into the drain-waste-vent system. As the name implies, the drain-waste-vent system removes solid, liquid or gas waste from the home through drains and vents. As the water empties from a sink, it goes through the p-trap, on to the drain line, and ends up in the sewage system.
Here is an overview of p-traps that you can reference when sink-related plumbing issues arise in your home.

What Is a P-Trap
In most homes, there is a P-trap installed under the sinks in the bathroom and kitchens. In a nutshell, a p-trap is comprised of a tailpiece, the curved trap piece, and a drain elbow. It is the u-shape piece under your bathroom or kitchen sink. The drain elbow for a p-trap fits into the drain pipe which goes directly into the wall. The P-trap traps debris that has drained from the sink and prevents it from forming a clog deep within the plumbing system, and to stops sewer gases from passing into the home. Under normal circumstances, p-traps always contain some water.
The P-trap can be made from PVC pipe or steel. Steel is used for exposed plumbing as it is more attractive but PVC P-traps are made of white plastic and last longer. Plastic P-trap contains nylon connectors that can be fastened by hand with the twist of the plastic nut. This makes it easier for most homeowners to fix it themselves.

What is a P-Trap Used For
The basic function of a p-trap is to ensure that wastewater is properly drained and freshwater is able to take its place. Each time one of your home’s drains is used, the wastewater is flushed through the drain’s p-trap and subsequently replaced by new water without any harmful gases or fumes finding their way into your drain. The p-trap is responsible for preventing noxious gases such as methane from making their way into a home.
P-traps are used for tubs, washing machines, sinks, and most other common household plumbing fixtures. P-traps will inevitably wear down and incur clogs over time, but fortunately, they are relatively easy to replace. These traps also allow homeowners to quickly and easily recover small items that fall down the drain.

How the P-Trap Design Works
A P-trap gets its name because it combines two 90 degree joints with a horizontal overflow pipe and gives the entire unit the shape of the letter “P.” One of the 90 degree joints exits the drain of the sink and then is joined to another which contains a water seal system that allows for water to flow into the overflow pipe, but not to flow backward toward the sink.
As water flows down the drain, the water level rises and flows down the drain pipe with accompanying waste to the sewage system. As the water stops flowing, the water balances out and new water becomes trapped again in the dip of the p-trap. This water eliminates space for any air or gases to flow back up through the drain.
The way P-trap safeguard is this: there is a water sealant in the curve of the trap that prevents sewer gases from returning into your drain while letting wastewater to pass at the same time; solids will stay in the trap so they can weaken. Anytime the trap is used, new water flows into the P-trap, dislodging out any remnants that may be in the trap part of the pipe.
Over time, a P-trap can wear out just like any other part of your plumbing system, and replacement may be essential. A P-trap that is not adequately serviced or installed can lead to a lot of problems for the sink it is fixed to, as well as other systemic issues; therefore, it is always essential to hire professional plumbers for P-trap work.

Common Problems with P-Traps
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.
Here are some common p-traps problems many homeowners can face:
Dry P-Traps
When the interceptor or trap loses its water seal, it provides sewer gases passage to re-enter the house via the drain.

Leaky P-Traps
The leaks often start small and quickly become a big problem if not fixed immediately. This leak frequently leads to a clogged drain, causing a foul odor. A leaky trap, like other faulty-ones, usually occurs as a result of a bad installation job.

Smelly P-Traps
Odors caused by p-traps are typically pretty bad. They occur when the sewer gases back up inside the home via the drain. If this problem is not addressed right away, it can eventually become hazardous for your entire family. Some common gases emitted by the sewage system include carbon monoxide, nitrogen, methane, and hydrogen sulfide. To avoid these, make sure to flush the drain.

Clogged P-Traps
Clogged/blocked p-traps happen because of slow-running drains. When these go unchecked, they are likely to cause leaks to seep smell into the house.

P-Trap Cleanout
Is your bathroom sink blocked, clogged, or not draining properly? The usual case is a blocked U-shaped pipe, commonly known as a P-trap. Clearing one of these plumbing fixtures is easy, and you do not have to be an experienced plumber to fix this issue.
If your home’s P-trap features an opening cap, all you may need to do it unscrew this cap, and pull any debris buildup out manually through the opening. This is a best-case scenario, and often, homeowners will have to go the extra length when their traps do not feature these caps, and physically detach their traps from the drain pipe.

Call the BEST Plumber for All Your Plumbing Needs
If you need help with your shower, toilet, sink, or any other plumbing issue, call Best Plumbing Services at 951-788-1321 for professional drain cleaning methods. Located in Riverside, California we are family owned and operated with over 10 years of experience. We take pride in our service and expect each job to be completed as if it were our own home or business. Our Licensed Plumbers and Technicians will be professional, clean and polite.