Replacing a Sink P-Trap

A How-To Guide

Sink Drain Trap
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A trap is installed in every type of plumbing fixture either internally or externally. They hold water and are used to keep the sewer gas smells from entering the building. The most common of these is the sink P-trap. This trap is installed under your kitchen and lavatory sinks of your home.

A sink P-trap is not only the most common trap, it is also the easiest to install or replace. Installing a new p-trap is an easy way to replace your drain if it is leaking, clogged, or just old and unsightly.

Most of the time the drain pipes under the sink can be either the white PVC or the black abs. Both of these types of pipe are easy to work with. If the pipes are going to be exposed then you can install a chrome P-trap so it will look nicer.

Replacing a sink P-trap:

  1. If you're are replacing your existing trap with a new sink P-trap first you have to remove the old one. Start by putting a small bowl to catch the water under the trap. Then disconnect the nuts on each side of the U-bend with pliers. Drop the trap straight down and empty out the water into the bowl.
  2. Now you can disconnect the trap arm by loosening the trap arm nut and pulling the trap arm straight out from the wall. Sometimes the trap arm can be a bit long and hard to pull out. Turn the pipe from side to side as you pull to help it along.
  3. Before installing the new p-trap prepare the pieces of pipe to make sure they will line up correctly. Start by laying all of the pieces out to help you get a better idea of what goes where.
  1. The first thing to install is the new trap arm. Slide a nut onto the arm facing down toward the trap area. Next, put another nut for the wall connection onto the pipe facing the opposite direction. Follow this with a slip joint washer tapered toward the back wall.
  2. Line trap arm up to where the trap will be to check the required pipe length. If it is too long you will have to cut it to size. It is normal to allow a portion of the drain arm to slide into the 1 1/2” drain pipe. Allow a minimum of 1” of pipe for this. More overlap is okay as long as you do not leave so much pipe that it will block off the vent or the drain pipe going down.

    Wait to tighten the nut on the trap arm until everything is in place as it will make the final adjustments easier.

  1. Slip a nut and the 1 1/4" washer onto the bottom of the pop-up drain with the washer tapered down. It is a good idea to put a bit of pipe joint compound on the face of both sides of the trap where it will seal. Put the p-trap straight up into position and hand tighten all of the nuts.

  2. If you find the piece between the trap and pop-up are too short then you can use an extension tailpiece that extends the trap. Also, this extension tailpiece can be used on the end of the trap arm is this needs to be longer as well.

  3. Once all of the pieces are in place and hand tight you can tighten the nuts a bit more with pliers. To check to leaks let the sink run. If you see any leaks try tightening the appropriate nut a bit more. Then stop up the sink and fill it with water then allow it to drain all at once. This is the real test.​