How to Install an Undermount Sink to a Granite Countertop

Undermount sinks look good with granite countertops. It adds a modern look to your bathroom or kitchen while simplifying countertop cleanup. Before we discuss the details of installing your undermount sink on a granite countertop, let’s first go through the general ideas of the project.

Granite countertops with undermount sinks

What Is an Undermount Sink?

Undermount sinks are defined by the way the sink is installed in relation to the kitchen countertop. Undermount sinks are installed under the counter, rather than being dropped into a pre-cut hole in the countertop.

  • Undermount sinks are defined by the way the sink is installed in relation to the kitchen countertop. Undermount sinks are installed under the counter, rather than being dropped into a pre-cut hole in the countertop.
  • Undermount sinks get dirty much slower than the regular ones because there’s no lip or crevices. Undermount sink’s hidden edge boasts stylish, streamlined looks.
  • Undermount sinks usually have single and double-bowl options. The most common materials used are cast iron, copper, and stainless steel.
  • Undermount sinks are more expensive than regular ones. Even though they don’t work very well with the laminate, they are greatly complimented by quartz, solid surface, and granite countertops.

What Are the Benefits of an Undermount Sink?

There are two main benefits of an undermount sink. The first one was mentioned above; it simplifies counter cleanup because it allows you to wipe food particles and any other dirt or grime directly into the sink. 

The second benefit is that undermount sinks are deeper than any other model types. The average topmount sink is approximately 5 inches deep compared to an undermount sink which is about 10 inches deep. This gives you more room for washing food and dishes in your sink. With that amount of room, you can even wash your small dog there if you want. So undermount sinks and granite countertops do belong together.

Choosing Countertops for an Undermount Sink

The best thing about undermount sinks is that they can be used with any type of stone countertop. Whether you have a marble countertop, a quartz countertop or a granite countertop, undermount sinks can be installed without any problems. Wondering how to install drop-in sink on granite countertop? Look through the guide below.

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We have a fabulous undermount granite sink project that will impress you!

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How to Remove The Old Sink

How to Remove The Old Sink

Before the undermount sink installation takes place, your old sink should obviously be removed. Don’t forget to take a picture of it, as you may need a reference later on.

Step 1

Shut the water down and remove the plumbing fixtures. Have a bucket and a mop or rag handy in order to remove any excess water that drips out. In the case you have a garbage disposal installed, shut down the power and remove it as well.

Step 2

Most of the time, the undermount sinks installation process requires a silicone sealant. Remove the old one with a utility knife and unscrew the metal clips that are attaching your sink to the countertop.

Step 3

If a faucet replacement is required, now is the best time to do it. As you will be working primarily under the sink, always wear protection goggles or glasses to ensure your safety.

Step 4

Now the kitchen countertop should be prepared for the new undermount sink installation. Use a razor scraper to remove all of the remaining silicone. Be careful, as you can scratch the countertop.

Step 5

To finalize the cleaning and prep work, apply alcohol to both the top and bottom sides of your countertop, as well as to the rim of your undermount sink.

How to Install Undermount Sink On Granite Countertop

Installing undermount kitchen or undermount bathroom sinks on a granite countertop might seem like a daunting task but it’s not as complex as it may seem. Hiring a professional may not even be necessary.


How to install undermount sink on granite countertop
Before starting your project, you will need to prepare a few essential items in order for the installation to go smoothly. 

Sink with mounting hardware

First things first, you should start with getting your undermount sink ready for installation. Make sure that your sink is the proper size for your countertop. Don’t forget to get every clip and mounting kit needed to install an undermount sink.


Have sandpaper handy for polishing the surface of your countertop and making the undermount sink installation process much easier. However, it’s completely optional if the surface of your countertop is already smooth.

Power drill

As the undermount kitchen sink installation requires clips, having a power drill is necessary to drill the holes in your countertop and adjust the position of the clips.


Even though the power drill works just fine, having a screwdriver is very important for this kind of job. You will be able to slightly loosen or tighten clips at any time without much of a hassle.


Using clamps will make the undermount sink installation much easier. This way, adjusting the position of your countertop will become much simpler for you.

Silicone sealant

Using a sealant is crucial for an undermount kitchen sink installation, as it will ensure the stability of the whole construction. We recommend using a silicone sealant, not only for its durability, but also for its water resistance.

Step 1

Measure the sink opening in your granite countertop. Normally, it will be 33 X 22 inches from outside the rims. Take the measurements with you when you go to your local home improvement center when it’s time for you to select your new sink.

Step 2

Choose a reveal style for your sink. This will determine how much of the sink’s rim stays visible after the installation.

  • Positive reveal – Part of the sink is exposed.
  • Zero revealed – The edges of the countertop opening are flush with sink walls.
  • Negative reveal – The countertop extends past sink walls.

Your choice of a reveal style should be based mostly on your preference but most people will go with the zero reveal. This type of reveal looks professional and leaves minimal space for dirt, grease, and germs to slip into.

Step 3

Center the sink to the opening on the countertop carefully. Align the rim of the sink to the edges of the countertop if you’re going for a zero reveal aesthetic.

With the undermount sink in place, mark the potions where the holes need to be drilled on the countertop. Take the sink out, and use a drill to put holes in the marked spots. Then clean the ridge with denatured alcohol and allow it to dry.

How to install drop in sink on granite countertop

Step 4

Next is to apply a thin layer of sealant to the sink lip and place the sink in from underneath. Adjust it into position under the granite. Be sure to use clear caulking when working on your granite countertop especially if the stone is dark in color. This will give it a cleaner and more professional appearance once the project is done.

Step 5

Insert the wingnuts into the available screw heads and make sure the nuts are tight. Wait for a few days for everything to set before installing the fittings.

Step 6

Attach the sink to the plumbing under the cabinet according to the manufacturer’s instructions. Remember to caulk around all threaded connections to create a waterproof seal.

Step 7

To ensure a tight seal, apply pressure on the sink from the top around the edges with your hands and press out any trapped air.

Step 8

Lastly, wipe away with a clean cloth any sealant or caulk that shows around the edges of the top of the sink.

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Things to Look at After Install

After you complete the undermount kitchen sink installation, it’s crucial to check if everything is adjusted and works as it should. Carefully examine everything, then pull and push the sink slightly to ensure that both the alignment and sealing are done correctly. Don’t forget to turn on the water to make sure that there is no leakage and that the water drains out properly.


When you have a negative reveal, a portion of the countertop underside is exposed to splashing water. This is a problem with granite countertops since granite is a porous material which means that water can seep through it and the sink area has a large chance of becoming a breeding ground for mold. To avoid this, make sure that your granite countertop is sealed on all sides.

Undermount sinks and granite counters

Another problem area is the gap between the sink and the granite. Even with a zero reveal, which means that the sink is attached to the sink as closely as possible, there is still a little bit of a gap that you have to caulk with silicone. This silicon caulk has the potential to build up food or grime over time. You have to take time every other week to clean this to avoid any germs from building up there.

Check for cracking or moldy caulking, and replace it if you see an issue. You are supposed to recaulk every three to five years to ensure that your undermount sink will last a long time. If taken care of properly, it’s going to stay there for life and it doesn’t weaken or damage your granite countertop the slightest. Undermount sinks on granite countertops are an asset to a home which is why it is so popular these days.

As with any DIY projects, it becomes a lot easier if you know what you’re doing. This means you have to read and research before you start installing your undermount sink to avoid big problems. Always be sure to read your instruction manual that comes with the sink and don’t be afraid to ask a friend to help you with the heavy lifting.

If you need help you can call Granite Selections to assist you in installing your undermount sink. To learn more about us give a call at (888) 906 3317.  We’ll be happy to help you!

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