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How to Install Undermount Sink on 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.

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.

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.

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
  • Power drill
  • Screwdriver
  • Clamps
  • Silicone sealant

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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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. Give us a call at (888) 906 3317 and we’ll be happy to help you.

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