What Is A P-Trap? (Sizes, Uses, Diagrams For Plumbing) (2024)

Instance 1

Plumbing traps prevent noxious sewage gases from entering your house by constraining gas or water in one particular place. There are various types of plumbing traps currently available for home or industrial uses.

However, none is as useful as the p-traps in plumbing systems. P-traps are pipes that ensure dirty water and toxic odors don't get access to your home, providing safety.

Page Contents (Click Icon To Open/Close)

What Is A P-Trap? Types & Sizes Explained

P-trap is a p-shaped bend pipe used in drainpipes to connect your sink's drain directly to the sewer system or septic tank. In usual circ*mstances, p-traps always retain some water.

They are made of cast-iron sheets or UPVC and have a robust water seal. One of the most crucial tasks of p-traps is to stop foul/noxious gases like methane from finding passage into the house.

These traps also make it quick and easy for homeowners to recover minor items that may fall into the drain. In a nutshell, p-traps play a consistent part in contemporary plumbing designs.

There are two main types of p-traps you'll come across: PVC and Chrome P-trap.

Chrome p-traps look aesthetically pleasing and ideal if you have a wall mount kitchen or bathroom sink. That's because these sinks are apparent and therefore should look beautiful to match the overall aesthetics.

They're suitable for high-temperature liquids and household acids. However, they are on the pricey side!

On the other hand, PVC p-traps use poly washers for joints and are incredibly tolerable to ultra-high temperature acids and liquids. Plus, they are a lot cheaper than chrome p-traps.

Lastly, although p-traps in the kitchen or bathroom sink work similarly, they are of different sizes. For example, the bathroom sink p-trap is usually 1 ¼ inch, while the kitchen sink p-trap is 1 ½ inch.

Role Of A P-trap: How It Works & Benefits

Modern plumbing experts advise consumers to always have p-traps under their kitchen or bathroom sinks.

They catch debris that falls into the sink, minimizing the chance of a choke. Other than that, these traps protect the overall plumbing system by preventing litter from draining deeper into the main pipes.

Another good advantage of installing a p-trap in the kitchen or bathroom sink is preventing sewage gases such as Methane, Hydrogen Sulphide, Nitrogen, and Carbon Monoxide from coming back into your house via the drain.

These benefits have made this the go-to pipe component for plumbing; it works to keep you and your family safe from a toxic environment.

The p-trap creates an organic water seal, letting water gush into the main overflow pipe; however, the water can't flow back to the sink.

It also prevents sewer gases from returning to the house through the backflow prevention properties of water seals (as it traps water).

Keeping these gasses at bay is essential because not only do they exude an unbearable odor, but they are also poisonous.

P-Trap’s Application: Where To Use

Legal plumbing codes require p-traps installed on every open drain to transport wastewater in the drain waste vent system safely.

Kitchens are no longer using s-traps as they tend to dry up. However, p-traps are a suitable option as they always maintain a consistent volume of water, and they are effective at keeping sewage gases from escaping through the sink.

Furthermore, they allow convenient removal of bulky morsels of food that slip into the drain. All you have to do is close off the water.

P-traps also excel in bathroom and toilet applications, as they offer efficient water sealing properties. Since they're available in various sizes (e.g., 1.5 inches in diameter), they are applicable in bathtub and shower traps too.

But that’s just not it; there are also HVAC and washing machine p trap applications. Since both these systems involve wastewater, it has to be drained out so that nothing seeps back in, be it gas or liquid.

It's convenient to fit them too because you won't be needing any extra tools for the job.

Check out the following p-trap diagram for various applications:

Bathroom Sink P-Trap

What Is A P-Trap? (Sizes, Uses, Diagrams For Plumbing) (1)

image source:HomeDepot

Kitchen Sink P-Trap

What Is A P-Trap? (Sizes, Uses, Diagrams For Plumbing) (2)

image source:HomeTips

Bathtub And Shower P-Trap Drain

What Is A P-Trap? (Sizes, Uses, Diagrams For Plumbing) (3)

image source:Kitchen Bed & Bar

Toilet P-Trap

What Is A P-Trap? (Sizes, Uses, Diagrams For Plumbing) (4)

image source:Hammerpedia

Washing Machine Drain P-Trap

What Is A P-Trap? (Sizes, Uses, Diagrams For Plumbing) (5)

image source:Pinterest

Air Conditioner HVAC P-Trap

Common P-Traps Problems

It's essential to get it professionally laid into the system. Incase a p-trap isn't installed correctly, it can damage and leak poisonous sewer odors into the house.

Here are some common p-traps problems many homeowners can bump into:

  • 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 snowball into a big problem if not fixed straight away. 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
    Smelly p-traps are often the worst. They occur when the sewer gases back up inside the home via the drain. If this problem isn't addressed urgently, 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.

How To Replace & Install P-Traps: Plumber's Tips & Techniques

Before knowing how you can replace or install p-traps in your sink, you need to prepare some essential equipment for the job.

Here's what you'll need:

  • Bucket
  • Rags
  • Work light
  • Tongue-and-groove pliers
  • Pip or hacksaw cutter
  • Drain kit

Now, follow these instructions to install or replace p-traps:

Prepare Work Space

Place a small bucket below the trap. Also, have some towels or rags ready for cleaning spills. Since the space below the sink can be cramped and dark, a flashlight or work light will come in handy.

Remove Trap Bend

Remove the old bend (curved piece) by loosening the slip nuts from both ends. Try easing them off with your hands and then use pliers.

Pull the bend and cautiously drain its contents.

Remove 'The Arm' Of The Trap

Loosen the slip nut first and then carefully pull the arm out. If it's stuck, spin it back-and-forth till it comes undone.

Test-Fit New Trap

Test-fit your new trap arm and bend to ensure they will align with the wall pipe and tailpiece.

If required, cut down the new arm to equal the length of the previous one using a pipe cutter; this will provide an exact fit.

Position The Washers And Nuts

Fit the slip nut into your trap arm and washer in the end. Make sure the washer bevel faces outward.

Gather The Parts

Slide the trap arm onto the drain opening. Now, fit the bend over the arm and sink tailpiece. Next, slide the nuts against their fittings and thread them over the hubs.

Lastly, adjust the trap and bend to align correctly, and ensure that the arms go downwards against the wall. Tighten the nuts by hand first and then with pliers.

Check The Fittings

Turn on the sink faucet to let the water run into the drain, allowing you to test the nuts for leaks.

To know more, check out this YouTube tutorial that covers all the steps in detail.

People also Ask (FAQs)

What is the difference between p-trap and s-trap?

The main difference between p-trap and s-trap is the length of pipe used. P-traps are p-shaped and designed to exit via a wall, while S-traps are s-shaped and intended to go through the floor.

How is p-trap different from j-trap?

The only difference between J-trap and P-trap is of the shape and nuts. While p-traps have removable nuts, a j-trap requires captive nuts.

How do you connect the p-trap to a wall drain?

Here's what you need to do: slide the shorter side of the p-trap over the tailpiece. Now, move around to line up the arm with the wall's opening.

Use a pipe cutter to cut the tailpiece if the p-trap isn't moving upward anymore, and that's all!

How do you convert an s-trap into a p-trap?

You can convert an s-trap into a p-trap by cutting its adapter off, or you can purchase thin-wall fittings; however, you will have to extend its pipe up.

How far can p-trap be from a shower drain?

Anywhere between eight to twenty-four inches is the ideal distance between a p-trap and a shower drain.

What will happen if p-trap is lower than the drain pipe?

It would be best not to have a p-trap under the drainpipe as water gravity will naturally force water out rather than flowing it downwards.

What is the minimum distance off the p trap to drain?

Eight inches is the minimum distance of the p-trap to drain.

What is the maximum horizontal distance of the p trap to drain?

The maximum horizontal distance of the p-trap to drain should never surpass 30 inches.

Conclusion

Plumbing traps are essential fixtures that every house requires, mainly because your sewer can discharge deadly gases harmful to your entire family.

P-traps are now the go-to pipes for drains, as they are efficient at blocking poisonous sewer gases. Furthermore, they are simple to install and wouldn't cost you an arm and a leg.

What Is A P-Trap? (Sizes, Uses, Diagrams For Plumbing) (2024)

FAQs

What are P-trap sizes? ›

Traps come in 1-1/4 inch (standard bathroom sink) or 1-1/2 inch (standard kitchen sink) inside diameter sizes. Be sure to check so you get the right size replacement at your local store. In this guide we'll show you how to replace a P-trap in a few easy steps.

What is a P-trap in plumbing? ›

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.

How do you know what size P-trap you need? ›

If you have 2.5 inches from the bottom of the tailpiece to shelf and 0.5 inches from the drain to shelf you can use CP-trap. First you have to cut 2.5-2.0 inches from the end of the tailpiece. The height of the p-trap is 4.5 inches 5-2.5=2.5 inches or 4.5-2.5=2.0 inches.

When you are installing P-trap what size of pipe you will use and why? ›

Each “P” trap shall have a water seal of not less than 2 inches and not more than 4 inches and shall be set true to its seal. (6) Size. Traps shall be not less than 1 1/4 inches in diameter. A trap shall not be larger than the waste pipe to which it is connected.

What size is P-trap pipe? ›

Your P-trap can be polypropylene (white or black), ABS (black), PVC (white) or 18-gauge brass (chrome-plated or natural). Plastic traps come in inside-diameter sizes of 1-1/4-in. for a standard bathroom sink; 1-1/2-in. for a laundry sink, bathtub or standard kitchen sink; and two inches for a shower or floor drain.

What is the minimum size of a trap? ›

P-506.2 Minimum Size

No trap or fixture drain shall be less than 1-1/4 inches, except as provided for in Section P904. 5. The fixture drains for water closets, trap standard service sinks and pedestal urinals with integral traps shall not be less than 3 inches.

Why is it called a P-trap? ›

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 ...

What are two main purposes of a P-trap? ›

A P-trap has three main purposes: trap debris, prevent clogs, and block sewer gas. Traps debris. The P-trap collects food, hair, and other waste that may clog drain pipes. By trapping the debris in the P-trap where it can be easily removed, it prevents costly repairs.

How does the P-trap work? ›

How Do P-Traps Work? | Spec. Sense - YouTube

How tall is a 2 inch P-trap? ›

CHARLOTTE PIPE 2 DWV P-Trap with Solvent Weld Joint DWV (Drain, Waste and Vent) (1 Unit Piece)
Size2 Inch ( EACH qty: 1 )
BrandCharlotte Pipe
ColorWhite
Item Dimensions LxWxH9.13 x 7.59 x 2.75 inches
Connector TypeTrap
1 more row

How long is P-trap? ›

Maximum Distance

According to the International Residential Code, the maximum vertical distance between the sink drain and the entrance to the p-trap is 24 inches.

What size is a typical kitchen P-trap? ›

They're generally 3 ½ inches in diameter and are larger than bathroom drains, which are 1 ¼ inch in diameter. Kitchen sink drains are the same size as most standard-sized shower drains.

How do you install a P-trap drain? ›

How to Install a Sink P Trap - YouTube

How do you install a new P-trap? ›

P Trap Replacement – Fix It In 15 Minutes | HouseSmarts - YouTube

How do you install a P-trap on a utility sink? ›

How to Replace a Sink Trap | Plumbing | The Home Depot

What size is a shower P-trap? ›

Under both the International Residential Code (IRC) and the Uniform Plumbing Code (UPC) the standard size for a tub drain and P-trap is 1 to 1/2 inches and under the IRC the tub waste arm (drain line) maybe 1 to 1/2 inches but under the UPC (Uniform Plumbing Code) a 1 to 1/2 inches drain line is limited to 1dfu ( ...

What is standard drain pipe size? ›

Toilet drain pipes are usually 3 inches in diameter. Washing machines and laundry sinks generally need 2-inch drain pipes. Shower and bathtub drain pipes are usually 2 inches in diameter. Sinks usually require a 1.5-inch drain pipe.

What is the best material for a P-trap? ›

The most common is plastic, which is made of either PVC or ABS. They are easy to install and maintenance is easy to perform. The plastic P-Traps are the least expensive of the two but is not as attractive as the metal traps. take apart to clean or service.

What is the diameter of a trap? ›

P-traps in a kitchen or sink will work the same way, but they do have different sizes. Bathroom sink P-traps are typically 1 ¼ inches in diameter and kitchen sink P-traps are typically 1 ½ inches in diameter.

What is the minimum trap size for a kitchen sink? ›

Recommended drain trap sizes for different types of fixtures
FixtureTrap Size (in)
Dishwasher1 1/2
Drinking fountain1 1/4
Floor drain2
Kitchen sink1 1/2
9 more rows

Why P-trap is important in plumbing system? ›

A P-trap Prevents Odors

Water is trapped at the bottom of the curve -- hence the name. This small volume of water prevents sewer gases from entering your bathroom, sparing your nose from nasty odors and protecting your health.

Why does water stay in P-trap? ›

After water runs through the drainpipe, some water will remain in the curved section of the p-trap, stopped by gravity. This water works as a plug against sewer gas that tries to drift back up the sewer line and into the house. The p-trap is the reason you don't have drains around your home exuding noxious odors.

Where is the P-trap located in a toilet? ›

A toilet trap, or trapway, is a curving channel inside the base of a toilet that leads from the hole at the bottom of the bowl to the drainpipe. When a toilet backs up and the clog did not occur in the drainpipe, the stoppage usually exists in the trap.

Is P-trap necessary? ›

A P-trap is required to be installed in most sink, shower, and bathtub drain lines by law. The reason P-traps are so essential is because they retain clean water in the drain line. This water seal stops horrible-smelling sewer gas from coming back up the drain line and into your home.

Where is the P-trap in sink? ›

The P-trap is the P-shaped section of pipe in the line that runs from the bottom of your sink to the wall. It's shaped this way to trap sewer gasses and prevent them from coming out the sink as well as to catch debris that's been washed down the sink, such as hair or food scraps.

What is the P-trap under the sink? ›

P-traps are U-shaped pipes in toilets and underneath sinks. P-traps hold a small amount of water that prevents sewer gases from rising up into your home. These pieces of plumbing also serve several other important purposes.

How do you tell if P-trap is working? ›

Is your P-trap working properly? If you detect any foul odors near the P-trap that remind you of a smell similar to rotten eggs, then it means that there is hydrogen sulfide present. This, and other harmful gases, bacteria, and viruses, can get into the house if your plumbing trap has malfunctioned.

How do you clean P traps? ›

Plumbing Advice : How to Clean a P-Trap - YouTube

How far can P-trap be from sink? ›

What is the minimum and maximum distance a P-trap can be below a sink? There is no minimum distance specified by the building code, but the maximum is 24” per International Residential Code (IRC) and Residential Edition of Florida Building Code (FBC 1002.1), measured from fixture outlet to trap weir.

How do you stop a P-trap from leaking? ›

Why is my Kitchen Sink P-Trap Leaking at Connection Nut?

What height should a sink drain be from floor? ›

The standard height of a kitchen sink drain from the floor is between 20 and 24 inches. This varies based on the vanity, sink, and trap.

How far can a P-trap vent? ›

Note: The developed length between the trap of the water closet or similar fixture and its vent shall not exceed four feet.
...
Distance of fixture trap from vent.
Size of Fixture Drain, InchesDistance Trap to Vent
1-1/23 ft 6 in
25 feet
36 feet
410 feet
2 more rows

How many P traps can one trap arm serve? ›

Not more than one trap shall be permitted on a trap arm.

How many fixtures can be on a 2 inch drain? ›

710.1 Maximum Fixture Unit Load
DIAMETER OF PIPE (inches)MAXIMUM NUMBER OF DRAINAGE FIXTURE UNITS (dfu)
Total for horizontal branchTotal for stack greater than three branch intervals
11/238
2624
21/21242
9 more rows

What is the most common size of PVC pipe? ›

As you might expect, it comes in different sizes. The most common sizes you'd use around your home would be 1½-, 2wo-, three- and four-inch. The 1½-inch size is used to capture water that might flow out of a kitchen sink, a bathroom vanity or a tub.

What is the standard drain size for a bathroom sink? ›

While a bathroom sink's design and overall size may vary from one model to the next, the drain holes are fairly standard, 1.25 inches being a general standard, with widths of 1.5 inches and 1.625 inches also common. The size of the hole helps determine which size drain is needed for that particular sink.

How do you remove a P-trap from the wall? ›

To remove the P-trap from the wall stub, hold the trap assembly firm with one hand and turn the coupling nut counterclockwise with respect to the wall stub until it comes loose. If the nut is overtightened or old, you might have to use a wrench or a pair of pliers for the purpose.

What is a dry P-trap? ›

A dried or empty plumbing trap, or P-trap, is one of the first causes to look for when the bathroom drains smell foul, especially if it has been lying unused for long.

What is the minimum length of a trap arm? ›

The minimum trap arm length is two pipe diameters, as measured from the trap weir to the vent (not between the hubs of the fittings). So a 1-1/2” pipe would require a 3” minimum trap arm, and a 2” pipe needs a 4” minimum trap arm.

Are #2 traps big enough for coyotes? ›

From left to right: Three sizes of coyote trap: No. 1.75 with 5 inches of jaw spread; No. 2 with 5-1/2 inches; No. 3 with 6-1/2 inches.

What size trap is a MB 550? ›

The MB-550 2 Coil Offset trap has an outside jaw spread of 5 1/2” and an inside jaw spread of 4 3/4”. The cast jaw face is 3/8” thick and the offset is 3/16”. Installed with a Paws-I-Trip pan system and stainless steel night latch dog.

What size traps to use for coyotes? ›

Foot-hold traps ranging in size from #1.75 coil-spring to #3N long-spring with offset jaws work well for capturing coyotes. Traps without offset jaws may cause foot injuries and increase the risk of escape. Conibear traps are not recommended because coyotes may avoid them and non-target animals can be killed.

Top Articles
Latest Posts
Article information

Author: Terrell Hackett

Last Updated:

Views: 6461

Rating: 4.1 / 5 (72 voted)

Reviews: 87% of readers found this page helpful

Author information

Name: Terrell Hackett

Birthday: 1992-03-17

Address: Suite 453 459 Gibson Squares, East Adriane, AK 71925-5692

Phone: +21811810803470

Job: Chief Representative

Hobby: Board games, Rock climbing, Ghost hunting, Origami, Kabaddi, Mushroom hunting, Gaming

Introduction: My name is Terrell Hackett, I am a gleaming, brainy, courageous, helpful, healthy, cooperative, graceful person who loves writing and wants to share my knowledge and understanding with you.