Project Book: How to Replace a Sink Drain Trap

By: Matthew Hersee

For those who are new to the world of plumbing, the word “drain trap” — also known as a p-trap or plumbing trap — may sound like a strange term. Despite the odd name, it’s one of the hardest working pieces of the drainage system under your sink. There are drain traps on your toilet and bathtub as well, but we’ll cover those later. A plumbing trap is a “U” shaped section of pipe underneath your sink drain that holds a small amount of water inside. This water creates a seal that blocks any foul odors from coming back up the pipes and into your home, if they do come into your home, then you may need to do some septic tank pumping.

Like most things in the home, drain traps have the ability to wear out or break, which causes two problems: It can leak, possibly causing water damage, and it can allow foul sewer odors into your home. Fortunately, a drain trap can be replaced simply, and safely. Let’s learn how!

ProjectBook: Replacing a Drain Trap
Difficulty: Medium
Estimated Time: 1-2 Hours
What You’ll Need for This Job:

TOOLS:	MATERIALS:
Hacksaw Slip Joint Pliers	Replacement Trap Small bucket

Step 1: Prep the Area

Bucket under drain trap — Place the bucket right under the drain trap

Start by turning off the sink and all water coming into the sink. Depending on the model of sink you have, you may have a shut of valve underneath the sink. If there isn’t one beneath the sink, then head downstairs to the main water line and shut it off there. After the water is shut off run the sink until water has been cleared from the lines, just in case you leave the project space for a few minutes and someone comes along and turns on the faucet.

Once the water is shut off, throw your bucket underneath the existing drain trap. There is water inside of the trap, and once we pull it apart, it will drain into the bucket. You can also stash the broken drain trap here.

Step 2: Remove the Old Drain Trap

wrench on slip nut drain trap — Use a wrench or channel-lock pliers to remove the nut

If your old drain trap has a drain knob on the bottom, undo it now and let it drain.

Using a pair of channel-lock pliers, loosen the nuts on the top and bottom of the drain trap. They may be on there pretty tightly, so you may have to use some force to get them loose. Be careful during this part to avoid cracking the tail piece, which can happen if your pliers slip too hard. Once the nuts are loose, unscrew them by hand and carefully remove the drain trap, allowing the water to drain into the bucket, and place the old trap into the bucket as well.

If you have not purchased a new trap, clean the trap out with gloves and bring it with you to your nearest Koopman Lumber store. You will want to get a trap kit that best replaces your current one, both in size and material. If you have an old chrome trap consider replacing it with an ABS or PVC trap. they corrode much less quickly than a chrome one and are a much better buy.

Step 3: Install the New Drain Trap

The new drain trap should easily fit into place. If it doesn’t fit, then it’s time to get out the hacksaw. Mark the exact length needed with a pencil, and then clamp the pipe down to cut. Work slowly and precisely to get the proper cut. Once cut, run sandpaper over the end to eliminate the burrs left on the pipe end.

installing new drain trap koopman — The new trap should fit right into place

Wrap the threaded ends with Teflon tape. Put the new drain trap in position and slide the nut over the gasket. Screw the nut over the sink’s tailpiece and hand tighten. Screw the other nut (hand tightened as well) over the drain stub. Use a wrench or your channel-lock pliers to tighten the new trap further into place. Be careful not to over-tighten, or you could break the pipe!

If the nuts are cross-threading repeatedly you will need to replace the nut, as the threads have been damaged too much to use safely.

Step 4: Test the New Trap

running-sink-drain-trap-koopman — Run the sink for a few minutes

Turn the water back on and slowly run the drain. Check for leaks, and if you find one tighten the appropriate nut. If nothing is leaking, stop up the sink and let it fill with water. Once it’s full let it all drain at once. This is the true test, and if you don’t encounter any leaks then your job is done!

Wrap Up

We hope you enjoyed this quick project book! There are vast amounts of different sinks out there all with different plumbing setups, if you find anything out of the ordinary with your plumbing, or are afraid to bite into this without talking to an expert, then head on over to http://www.koopmanlumber.com. Our employees are experts at their job and can provide guidance for any projects you have. Thanks for reading!