Introduction: How to Install a Bathroom Sink Drain

About: DIY Montreal is all about woodworking & DIY projects. I post how-to videos on my YouTube channel, as well as step-by-step tutorials on my website Builds include mainly woodshop project…

In my last tutorial, I showed you how I built a floating vanity for my powder room. In this DIY plumbing tutorial, I’ll show you how to install the sink drain, namely the P trap.

If you also want to see how I installed my wall faucet and vessel sink, watch the video above.

There are 3 parts you’ll need when installing a new sink drain: a P Trap kit, a trap adapter, and a pop-up (or regular) sink drain assembly.


Step 1: Install Pop-up Drain

The pop-up drain assembly typically comes with your sink or can be purchased separately as a kit.

To ensure a watertight seal, I’m applying a bead of silicone all around the drain pipe. Make sure to use 100% silicone and apply a generous bead before dropping the drain into the sink hole.

From underneath the sink, I added the rubber ring, by first adding a dab of silicone to the threads to help it twist on smoothly.

Next, just as per the assembly diagram, I added this plastic ring and a nut that I’ll first hand tighten and then give it another quarter turn using some slip joint pliers to tighten it up.

Once everything is fully tightened underneath, you’ll want to make sure to wipe off any silicone squeeze out from the drain and the sink using a clean damp rag.

I can now attach the last part of the pop-up drain assembly, which includes a rubber ring that will create a seal with this smooth metal pipe. For now I’ve only hand tightened the nut but I’ll come back later with some pliers to tighten everything up.

Step 2: Install P Trap Adapter

For a new sink installation you’ll typically have a piece of pipe sticking out of the wall. In order to connect the P trap you’ll need a trap adapter that needs to be glued onto the pipe in the wall.

Since my pipes are ABS I’m using ABS cement. I simply swab the inside of the trap adapter with some cement and do the same for the outside of the drain, making sure to fully coat both surfaces, then push on the adapter, all the way in, giving it a slight twisting motion, roughly a quarter turn.

Step 3: Install P Trap

While the cement dries let’s take a look at the P trap kit. All of these parts typically come in the kit: the waste drain, two plastic or rubber washers, and two slip joint nuts.

Start by connecting the 2 black pipes. You simply slip a nut onto the waste drain and press it against the other pipe, then hand tighten the nut. No washers are required here.

Next, find the washer that will fit onto the drain under the sink. You’ll note one of them is much too loose, but the other one fits just right. Place a slip joint nut on the pipe first, followed by the washer.

Tip: It’s important to note the orientation of the washer when using slip joints: make sure the tapered side is facing whatever you’re trying to connect to.

Next, connect the waste drain to the wall. Your pipe may be too long, and can be cut using a hacksaw.

Once the waste drain is cut, slide on a slip joint nut facing towards yourself, then another nut facing the wall and lastly the remaining washer, tapered side towards the wall. Insert the pipe into the wall and screw it onto the adapter.

Lastly, add the U shaped pipe and connect the slip joint nuts on each end, again loosely tightening and adjusting the parts as needed to make sure everything lines up without stressing any of the joints. If your parts don’t line up and you find yourself forcing a connection, you’ll likely end up with a leak.

Once everything is aligned, hand tighten all of the nuts. After that I used some slip joint pliers to tighten them up a little more so that they are nice and snug, making sure not to overtighten.

Step 4: Test for Leaks

The last step is to test the drain for leaks. I first let the faucet run and check the pipes for leaks.

Everything looks good so far so I’m going to put it to the ultimate test by filling up the sink all the way and then draining it out. I repeated this process a few times.

No leaks! What a relief. If you did have a leak, try tightening the leaky joint a little before testing it out again.

If you haven't already, check out the video for more details.


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