Rogelio Alvarez

By: Rogelio Alvarez on February 20th, 2023

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What Is a P-Trap?

If you ever accidentally drop a piece of jewelry in your drain, don't panic! Thank the p-trap's design for catching it before it gets lost in the sewage forever. 

P-traps are amazing for catching things from going down the drain and causing serious clogs or lost wedding rings. But have you thought about what they prevent from coming up? They also help trap sewage gas from leaking into your home.

For over 15 years, we at Monkey Wrench Plumbing, Heating & Air have inspected, maintained, and replaced hundreds of p-traps across Los Angeles and the surrounding cities. We understand the importance of the p-trap both as homeowners and plumbing technicians. 

Our accumulated knowledge of p-traps can help you better understand and maintain your home's fixtures. Once you're done with this article, you'll have a clear understanding of the following:

  • How P-Traps Work

  • Different Types of P-Traps

It's time to roll up your sleeves and immerse yourself in the world of p-traps!

What Is a P-Trap Used For?

A p-trap pipe was designed to prevent sewer gas from backing into homes. It is called a p-trap because it is shaped like someone flipped the letter P and laid it down. Its design creates an airtight seal by holding enough water in the curved section.  

Here's a more in-depth explanation of how p-traps work.

  1. Water from kitchen and plumbing fixtures falls and fills out the curved portion of the p-trap.

  2. The water trapped in the bend creates a seal that stops gasses from leaking out.

  3. The seal prevents sewage gas from entering your home.

  4. The arm of the p-trap is connected to an outside air vent that extends from the top of a home. The other end of the connection leads toward the sewer line.

  5. Water will travel through drains as the fixtures are used, but the p-trap will always retain enough water to keep the seal. 

Without p-traps, gasses from the sewer line will stink up your home. P-traps are also necessary to stop objects from entering your home's pipes and causing troublesome clogs. Sewer gas exposure may also cause a person to experience various symptoms, such as nausea, dizziness, headaches, and fatigue. 

P-traps are required in every residential building, according to the United States Department of Housing and Urban Development. The regulation also states that full s-traps are prohibited. 

S-traps look like the letter “S” laid on its side. These traps are no longer used in plumbing because the water can get siphoned and unseal the trap causing sewer gas to leak. If you have an older home and suspect you have a s-pipe, click to make an appointment below


So you know how p-traps function, but did you know that they're available in different materials?


Types of P-Traps in Plumbing

The design and function of the p-trap are the same regardless of what material its made of. The type of material chosen for p-traps varies from homeowner to homeowner. Each material has its advantages and disadvantages but will always retain its function as a p-trap.  

The p-trap in your home is most likely made from one of the following materials. 

  • ABS (Acrylonitrile Butadiene Styrene): ABS pipes are always black, so if you check under your sink, for example, and see a black p-trap, it's made out of ABS. These plastic pipes are weak to sunlight, so they’re commonly used indoors. 

  • PVC (Polyvinyl Chloride): PVC pipes are a plastic material colored white when used in plumbing systems. Common in plumbing, PVC pipes can be shaped to fit and connect with plumbing pipes in your home. P-traps are commonly made out of PVC. 

  • Brass: Brass is goldish and used to make p-traps and other plumbing pipes. Although not as common as plastic p-traps, some homes can have brass pipes in their plumbing. Brass is a durable material but is less preferable in plumbing than other steels like galvanized steel. 

  • Galvanized Steel: This pipe material is known for its corrosion resistance. Its resistance makes it a popular choice for p-traps, but it's also more costly than plastic pipes. 

  • PP (Polypropylene): A durable plastic pipe, PP p-traps are less expensive than stainless steel. Although this material is lightweight, it is not as durable as other plastics, such as PVC. 

Although there are plenty of do-it-yourself videos and instructions on replacing your home's p-trap, it is recommended to seek a professional plumbing company in Los Angeles to help you replace it without any issues. 

You're becoming more familiar with p-traps, but do you know where in your home they're located?


P-Trap Sink

Every sink in your home, whether a bathroom or kitchen sink, has a p-trap underneath it. If you want to know what a p-trap looks like, look underneath any sink in your house. 

Sinks are the most common place to drop something down the drain accidentally. P-traps under the sink have a clean-out, making it easy to clear the water in the bend. This also allows you to remove anything that might have been stuck in the curve instead of removing P-traps completely. 


P-Trap Toilet

Standard toilets are already designed with a built-in p-trap, also known as a toilet trap. If you look at the toilet in your home, you will notice the p-trap design at the bottom back half. 

Toilets are one of the most commonly used fixtures in a home, so their p-trap is vital in keeping sewage odors away from your home. If your toilet is clogged, it could be located in the p-trap. Most plungers can unclog the p-trap in the toilet so it can continue to seal sewage odors away. 


P-Trap Shower Drain

Whether you have a standing shower or bathtub, it will always have a p-trap. The p-trap for showers is located underneath. Like the other fixtures, the shower drain p-trap prevents sewer odors from escaping your pipes.

Shower drain p-traps are not easy to access on your own, and you should speak directly with a technician for further assistance. Clogs in the shower drain p-trap can be cleared with a drain snake. Drain snaking is a helpful service in unclogging p-traps, but its costs vary on different factors


P-Trap Floor Drain

Some homes have floor drains outside or near their washer machines. These drains do a great job of clearing the water gathered from the rain, sprinkler overflow, or a hose. 

P-traps require trapped water to seal off sewage odors, so it's important to keep your floor drain from drying out. A dried-out p-trap doesn't have a seal, so it won't protect your home from leaking sewage odors. It is recommended to run water down these drains periodically, especially in the summertime, so they stay sealed. 

Now You Know How a P-Trap Works

Thanks to their function as a barrier for sewer odors, p-traps are the MVPT (the most valuable plumbing tool). We highlighted how vital their role is across different home fixtures and the other materials they're available in. 

At Monkey Wrench Plumbing, Heating & Air, we are fully aware of the vital functions of p-traps, but only some homeowners know this information. We are not only great at replacing these pipes, but we also believe in sharing information about them, so homeowners better understand the plumbing in their homes. 

If your home's entire plumbing, not just p-traps, can use an overhaul, take the time to learn about the cost factors behind this project

If you have any questions or experiencing any concerns with your home's p-traps, call us or book an appointment online