How to install undermount bathroom sink

How to install undermount bathroom sink

If you encounter any problem with how to install undermount bathroom sink, no need to worry because that is what I am going to show you. Usually, under-mount bathroom sinks are very simple and easy to install compared to kitchen sinks. However, you need to take into consideration some precautions during the process.

Therefore, without wasting too much time in the introduction, let me consider the well-researched definition of a bathroom sink. After that, we can comfortably look at the steps involved when installing small undermount bathroom sinks.

undermount bathroom sink

What is a bathroom sink?

Bathroom sinks are tools which consist of countertops with integrated cabinets and pre-drilled to fit appropriately onto different faucet configurations or even undrilled for customized installations of the faucet. Most of the bathroom sink consists of Enameled cast iron materials, which enhances durability.

How to install undermount bathroom sink step by step guide


The following are some essential equipment that you need for the effective installation of your undermount bathroom sink. They include;

Utility knife
80 grit sandpaper
Bar clamps
Caulking gun
Nut driver
Transparent silicone resin adhesive
Electric drill
Mounting tape
Screw gun

Step one: start by making the space for your sink top on the counter

Basically, under-mount bathroom sinks are somehow different from the rest of the sinks. Therefore, they require you to create a specific hole on the counter for quick installation.

Besides, these undermount bathroom sink comes with various types and sizes, which you need to have them before you resume cutting.

To make a perfect space, start by measuring the length and breadth of your sink accurately and compare it using the measurements provided in the instruction manual guide book. For accurate measurements, flip your bathroom sink as you make some marks on the exact place of the drill to enable you to cut precisely the space of your sink in its countertop.

Once you have the correct measurements, you can comfortably start your cutting process. Sometimes you can get some assistance from your friends and family members. Ensure that you use an electric drill with the saw when cutting the same region for your sink.

Read Related: Pedestal sink

Step two: prepare the countertop

Now that you have your space ready with you, it is time to prepare the countertop where you can mount your undermount washbasin. However, you need to do some prior tasks before attaching them. The first thing you do is to smoothen the corners of the hole using sandpaper to prevent any damages to the sink.

Next, grab a clean cloth or even a regular wet cloth and remove all the dust and any other stains on the countertop. Once the top is clean, use acetone and wipe across the edges of the countertop to remove any specks of dust or debris which may otherwise affect the adhesive prowess.

Then you can wait for some time so that the wood and granite dry up after cleaning to prevent the adhesive from working on the wet surface.

You can now flip the countertop and make some marks where you would wish to mount the sink. Use the electric drill mentioned above in making a hole where you will attach the clamp and use acetone to clean on the surface of the hole to smoothen the surface.

Using a caulking gun, apply enough latex or silicone on the edges of the undermount basin. For safety purposes, you can put enough silicone at the edges of the hole on the countertop. Next, carry your undermount sink, place it carefully on the countertop, and ensure that its position is at the center.

Once your undermount sink settles on the countertop, you can put the mounting clip to secure the sink’s pan’s position firmly. Mounting clamps are usually metal clips that are useful in holding the washbasin that are heavy without damaging the countertop.

After successful mounting of clips, allow the basin to settle for about eight hours for adhesive dryness. However, if you are not in a hurry, you can enable it to settle for 20 hours.

After successfully installing the sink in the countertop, you can now fix the newly purchased faucet as you put the tap onto the counter. Next, make some holes where you will be inserting the faucet using the handsaw and drill.

You must be very keen at this step when making a hole because if you confuse even a single inch, you may create a big gap that may hinder your installation.

Step three: putting your sink in place

At this step, you can flip the countertop with your sink attached from the bottom once the adhesive dries up completely. However, before flipping the countertop, you can apply enough silicone at the counter’s base using a caulking gun. Remember to apply a thick layer of silicone at the counter base for proper attachment to the top shelf.

Immediately you complete placing the countertop on the base counter. You can comfortably install the faucet to the hole. You can start by attaching the rubber or plastic on the table and then put the tap onto it. You can now use a nut in bolting the faucet with the help of a wrench to secure them properly.

Step four: assemble the lines

At this stage, you need to connect the entire water lines to complete the whole setup. To succeed on this, you can begin by attaching the drain opening with the drain line using the connectors in sealing the connection regions.

You can hook the water lines to the faucet, bearing in mind the one for hot and cold water without getting any confusion. Ensure that the alignment of the water line is correct for reasonable force. Once everything is in place, you can test the water flow by turning on the knob and opening the faucet.

Frequently Asked Questions

What is the best undermount bathroom sink?

The best undermount bathroom sink is the KOHLER Archer High-end bathroom sink because it has the highest ratings.

What are the different types of bathroom sinks?

The different types of sinks include;

Undermount sinks
Self-rimming sinks
Wall-mounted sinks
Vessel sinks and
Console sinks


Having gone through this article, I hope you have insight information on how to install undermount bathroom sink correctly without any stress. However, if you face any problem like leakages, you should tighten that section with a screw or use tape to seal them permanently.

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