How to Seal a Bathroom Sink Drain? Silicone Caulk vs. Plumber’s Putty

Sealing a bathroom sink drain without calling a plumber requires proper skill. When I needed to fit the sink drain, I followed all the standard procedures but when I tested the water flow, there was leakage. Then I discovered I didn’t use any extra sealants such as plumber’s putty or silicone caulk to seal the drain leakage.

But, which sealant is best to seal the bathroom sink drain?

Plumber’s putty and silicone caulk are both good sealants for leaking sink drains. Although both will create a good seal, plumber’s putty is preferred for sink drain flanges while silicone caulk provides the best seal between the edges of the sink and the countertop.

Some plumbers prefer plumber’s putty when installing sink drains, while others use silicone caulk because they have modern waterproof material.

I’m going to dive deep into how to seal a bathroom sink drain properly in this article. I’ll also compare which sealants should be used and how to use them properly.

Seal a Bathroom Sink Drain

How to Seal a Bathroom Sink Drain

There are four parts of your drainpipe. The cap or flange sits on top of the sinkhole. And the tailpipe goes under the sink and meets the flange from underneath. There’s a gasket and a nut on the tailpipe to properly join them together. You can tighten the nut against the gasket to seal it.

But this doesn’t always provide adequate sealing and water keeps leaking. That’s because you need a good sealant to sit on any joining bodies. Sealants seal any possible gaps and create a robust joint. Let’s see how to seal a bathroom sink drain with the help of silicone caulk.

Step 1: Remove Old Sealants

You should always start from scratch and remove the old residues before sealing the sink drain with silicone. You can remove the old one by loosening the lock nut and removing it. Now the drain is detached. This enables you to access the insides and remove the sealants.

You can use a knife or small spoon to remove and clean up the drain area. If you’ve previously applied putty on the area, you can use a putty knife to remove them.

On the other hand, if you have a silicone sealant, you might need to use chemicals to dissolve it. Alternatively, you can apply vinegar to loosen it. After removing the old sealant, you can proceed with a new layer of silicone sealant.

Step 2: Applying Silicone Caulk

Silicone caulk is used as an adhesive sealant to seal a bathroom sink drain. They’re water and temperature resistant. You need to get a good silicone caulk from the market. Then, apply the caulk by directing it and pressing the tube gently. The first layer goes around the sink drain hole and the second layer goes on the drain flange.

You can use your finger to firmly spread the layer of silicone caulk along the lines. But the silicone caulk gets stuck with the fingers. To avoid it, use a sprayer bottle of water with some detergent inside.

Apply the mixture to the silicone bead and apply some on your finger as well. This prevents the silicone to get stuck on your fingers, giving you more control.

As you’ve applied the silicone caulk perfectly, now it’s time to assemble.

Step 3: Join the Flange

I’ve applied a silicone bead beneath the drain flange. Now I can join it with the drain hole which was also applied with a layer of the bead.

To do that, just put the drain flange inside the drain hole. Align perfectly and put some pressure on it by pushing it further inside. As you apply pressure, the silicone bead within the two parts starts to seal the gaps tightly. This ensures there is no gap. Now, all we need to do is to screw the gasket.

Step 4: Join the Gasket

Gasket seals and holds two parts together. This goes under the sink. You need to press the flange and place the gasket under the sink simultaneously. When in place, you can now fix it with the lock nut and then tighten it to seal the drain in bathroom sink.

While tightening the nut, start by tightening initially with your hand to keep it in place. Then to secure the joint, you need to use a wrench to tighten the lock nut strongly so that no movement is allowed and it sits perfectly.

The sealing part is complete, now it’s time to clean up the joint.

Step 5: Clean Up and Test

During joining, it’s common to use too much caulk in uneven places to reseal a sink drain. As you tighten the joint, excess caulk comes out. You can clean up the joint with water and a piece of cloth. This is important to prevent the possibility of corrosion.

After that, you can test the setup by running some water through the sink. Let it run and inspect if there are any leakages from where water is pouring out. If there’s a leakage, you need to remove the lock nuts and open up the pipes yet again. Check if sufficient caulk was applied there. Also, when joining, be sure to align them perfectly, otherwise tightening may miss a thread and you get a faulty joint.

Plumber’s Putty vs Silicone – Which One Should Use on Bathroom Sink Drain?

Plumber’s Putty vs Silicone

Both plumber’s putty and silicone are widely used forms of compounds that are used to create a plumbing joint free of leakages. To seal a bathroom sink drain, silicone caulk is a better choice. But it depends on your goals too.

We can use both the putty and silicone in the sink drain. But silicone caulk creates a stronger and more weatherproof sealing. It’s chemical-proof too. So, there’s less chance of it eroding if you pour some chemicals down the sink.

Silicone caulk is also used on any porous surfaces but plumber’s putty is only used for plumbing sealing. You can have a more versatile operation with silicone caulks.

However, silicone caulks are harder to remove once you apply them. So, it’s best to use the caulk in fixed places where you’re looking for durability. If you want more flexibility and easy opening, a plumber’s putty is still a great choice. They’re easy to remove and good for small areas.

The correct way of Applying the Plumber’s Putty on the Sink Drain Flange

Plumber’s putty is a soft clay-like material for sealing. And, it stays soft throughout its usefulness so that you can remove it anytime. To seal a bathroom sink drain with plumbers’ putty, you should check if the sink material is a compatible one for that putty.

When applying putty on the sink drain flange, create a circular rope with the putty around the sink. Ensure that there’s no gap on the putty circle, then press it with your finger to place it correctly.

After applying, you can now place the sink flange on the sink and force it. The excess putty comes out and the joint is fixed in place. Use a cloth to wipe the excess putty out of the place. This is the same for the silicone caulk as well.

Once the parts are in place, check visually and ensure that there’s no gap in the joining places. Test the joint by running water through the sink drain.

How to Test the Seal

We can easily test the seal by applying pressure on a blocked pipe. We can do this by using a rubber stopper and testing the water level.

Rubber stoppers or bung stoppers come with every sink. They’re used to seal and plug the pipe to create an enclosed sink. Place the rubber stopper on the pipe end to seal the end so that water can no longer pass. Then, start pouring water through the sink. As water can’t drain because of the stopper, it starts to fill the pipe and later, the sink.

After filling the pipe and a portion of the sink, stop and check if the blocked water level stays the same or decreases slightly. If the water level stays the same, there’s no leakage on your drain seal. But. If water starts to lose its levels, there’s a leakage. Remove the rubber stopper and free the water, then fix the seal again.


Here I’ve gone through the steps of sealing a bathroom sink drain. Before we proceed, we need to ensure that the old sealants are cleaned, otherwise, they might interfere with and weaken the new layers of sealants. Then we unscrew them and open up the joints. In between the joining bodies, we can now apply the sealants of our choice.

Silicone caulk is the preferred choice for a stronger and more durable sealing. But you can go for a plumber’s putty too if there’s the flexibility you need. Make sure the sealant is evenly applied, then force the flange on the hole together. Clean up excess sealants, and fix the joint by screwing the gasket with the nuts.

As the assembly is done, testing is just as important. You can test it using a rubber stopper and check the closed water levels. And you now have your joints ready to use. Sealing a bathroom sink drain is an easy job if you know these tricks and follow the steps accordingly.

Lisa Burks

This is Lisa Burks, the Author. I provide free informative sink and faucet guides. I hope you love your time here.

Recently Published