How To Connect P Trap To Wall Drain: 5 Installation Steps

Whether you’re replacing a plumbing trap or installing one under a new fixture, you’re probably wondering how to attach a P-trap to the wall drain if you’ve never done this before. Luckily, this task is easier to complete than you think. This guide will teach you how to do it in five quick steps.

How To Connect P Trap To Wall Drain

Here are five steps for connecting a P-trap to a wall drain like a pro: 

1. Gather The Necessary Materials 

While connecting the P-trap to a wall drain isn’t complicated, you need a few tools and materials to get the job done: 

  • Pliers 
  • P-trap
  • T fitting (optional)
  • Hacksaw 
  • New tailpiece 

2. Install The Tailpiece  

The tailpiece is a section of pipe extending from the sink drain and connecting to the P-trap. Not all sinks need one, but if you’re replacing a P-trap on a sink that has a tailpiece installed, you’ll have to remove the old part and replace it with a new one. 

As a rule of thumb, you will always need a tailpiece to connect a kitchen P-trap to the wall drain. To install it, slip the tailpiece washer into the flared end of the pipe and attach it to the sink strainer with the slip nut. Fasten the nut by hand as tightly as possible.

If your kitchen has a double sink, know that a P-trap can service both of them. In this case, you must install a sanitary tee on the tailpieces to connect them to the same trap.

Bathroom sink drains generally start as tailpieces. Depending on the position of the wall stub, the sink tailpiece may reach the P-trap without additional extensions. If you need an additional length, install a tailpiece, then cut it to dimension with a hacksaw.

3. Connect Tailpiece To P-Trap 

A P-trap consists of a vertical length of U-bend that connects to the tailpiece and a horizontal length of pipe called a P-trap arm.

The trap arm is connected to the U-bend with a slip nut that you can unfasten. For an easy installation of the P-trap, remove the arm from the U-bend, then connect the bend to the tailpiece that drops down from the sink drain.

When installing, make sure you’re connecting the long side of the bend to the tailpiece. Align the long arm opening with the wall drain, then connect the P-trap to the tailpiece fastening it with the slip nut – don’t tighten the nut yet. 

4. Connect Trap Arm To Wall Drain  

You can now connect the trap arm to the wall drain. Slip a washer on the trap arm and push the arm into the PVC or metal wall drain stub out. If the trap arm is too long, measure the correct length and cut the excess pipe with a hacksaw. Thread on the slip nut and tighten it by hand.

5. Connect P-Trap To Stub Out 

Align the U-bend with the trap arm you just connected to the stub out – you may have to slightly turn the bend left or right to achieve a proper alignment. When in position, thread the slip nut on the trap arm and tighten it by hand

You can now tighten the nut connecting the trap to the tailpiece. Turn on the water and wait for a minute or two, then check the trap for leaks. That’s it.

Installing P Trap Into Floor Drains (4 Steps)

Many of us associate P-traps with sinks because that’s where we see them. However, all plumbing fixtures are required by law to have a trap. The most important thing to do when attaching a drain to a P-trap is to achieve a proper P-trap configuration. Here’s how to do it.

1. Gather The Necessary Materials

  • P-trap
  • Floor drain
  • Plumbing glue
  • Pipes 
  • Couplings

2. Install The Drain 

Assuming you have already cut a drain hole in the floor, install the drain on the floor and screw it in place in such a way that the lower extension fits completely through the hole and extends into the floor below.

3. Install The Extender Pipe 

Cut a 12-inch section of ABS pipe and remove the burrs. Smear some plumbing glue on the outside of one side and push it into the floor drain coupling. Hold in place for about two minutes to let the glue set. 

4. Connect The Drain Pipe To The P-Trap 

Position the P-trap in such a way that its arm faces the main drain line (connecting to the house’s drainage system) in a straight line. Couple the P-trap to the extender pipe you attached to the floor drain and hold it in place for 2-3 minutes to let the glue set. 

If the main drain line is already installed, you can also couple the trap arm to the drain line by gluing it in place. 


Should P-trap be installed below the wall drain?

No, it is not ideal to have the P-trap installed below the wall drain because the water coming from the fixture would have to pump the water in the trap back up, forcing it against gravity. Ideally, the trap should be at the same level as the exit drain. 

Does it matter which way the P-trap goes?

Yes, it matters. When installing a P-trap, you must pay attention to its configuration and install it properly to avoid future problems. The short arm of the trap (the vertical one) must attach to the tailpiece. Installing the P-trap backward and attaching the short arm to the long arm (the horizontal one) can create numerous problems, including backflow issues and frequent clogging.

How far below the drain should P-trap be?

According to the International Plumbing Code, the P-trap should be located at no more than 24 inches below the sink drain. If the wall drain is located lower than this, you should raise it with an elbow and a vertical section of pipe that connects to the trap arm at the indicated height. 

Final Thoughts 

P-traps are essential components of all plumbing fixtures. Whether you want to plug a P-trap into a wall drain or install it into a floor drain, we hope this guide can help you achieve your purpose. Keep in mind, though, whenever you’re in doubt, the best thing to do is to call in a licensed plumber.

Recent Posts