Home > Blog > Home and Family

How to Replace an Undermount Kitchen Sink

Like other home design ideas, an undermount kitchen sink is pleasing to look at and makes a beautiful addition to all kitchen types. But though an undermount tub lasts long after installation, you may need to replace it for one or more reasons. In this article, you shall learn the steps to take when replacing your undermount kitchen sink.

Unlike a top mount kitchen sink, an undermount is tricky and hectic to install. A botched installation may end ruining your high quality countertop. You should also consider the weight of the sink and ensure the support is excellent during the installation. Here is a guide on how to replace your undermount kitchen sink.

Replacing an Undermount Kitchen Sink

Step 1: Remove the Existing Undermount Sink

If you are replacing your undermount sink, you need to remove the already existing sink. Use the right gadgets and equipment to unscrew and detach the sink from beneath the countertop. Be careful not to ruin the countertop in the process as it will make it hard to install another sink.

Step 2: Measure the Undermount Sink to install and the countertop's hole

Since there was another sink installed, it means that the countertop already has a hole where the sink settled. First, measure the countertop's hole and that of your sink to see if both match.

If the sink is larger than the hole's size, you need to cut it to fit the sink. But if the sink is smaller, then it may not work. The only solution is to get a tub with the exact size, or more significant where you get to increase the countertop's hole's size.

It is easier to measure the size of the existing sink to get a clue of the size you need to replace it. Also, measure its depth to avoid interfering with the space for its supporters stationed underneath.

Step 3: Install the Undermount Sink in the Countertop's Hole

When replacing your undermount kitchen sink, you may also opt to change the countertop. If that's the case, you need to first cut a hole in the new countertop to the size of the sink to install. Then flip over the countertop and install the sink while facing down. If using the installed countertop, install the right undermount kitchen sink from beneath.

For new countertops, consider your kitchen's water supply lines before cutting the hole to install the sink. Consider a countertop that works excellent with an undermount kitchen sink such as those made from stone and concrete. Countertops made using materials like laminate and wood may crack during the replacement of an undermount kitchen sink.

To get rim's width, use a pencil to trace the sink when flipped over. A sink's average is usually 0.95cm wide. Then from the first lines, make another outline. Then erase the first outline to avoid cutting it by mistake.

Some undermount kitchen sinks consist of cardboard templates. If yours has one, place the model on the countertop and trace the size. Remember, the outline should be smaller than the opening of the undermount sink. After installation, the sink's rim will rest against your countertop, and only the sink bowl will be visible. When cutting the countertop, use a jigsaw or circular jaw, and put on safety attire or gear like goggles and dust mask. Choose the saw based on the countertop's material.  A circular saw with a blade coated with a diamond will work out great with a stone countertop. A jigsaw is great for a laminate countertop.

If you don't have the right tools for cutting a countertop or have no idea how to do it, don't guess or use any device. Call a professional. Countertops are expensive, and it's not fun to have it destroyed. Use a drill to make holes to use with sink accessories like the faucet or soap dispenser. Also, consider a drill ideal for the countertop type. For example, masonry bit for the concrete or stone made countertop.

Step 4: Choose the Style of Your Undermount Kitchen Sink

The visibility level of the sink's rim after installation determines its style. Though it's essential for the look, it also affects its cleaning. Many people prefer not revealing the sink's lips for easier cleaning. In this style, the edges of the countertop get flushed with the opening of the tub. As a result, the sink looks professional and leaves no space for food particles or dirt to slip under the rims.

If you opt to reveal your rims, the sink will look great and improve the room's appearance, but you'll have a hard time cleaning under the sink's rim. A lot of dirt will hide and stick under the sides, and removing them is an uphill task. As a result, the dirt pills up, making the area filthy and prone to bacteria and germs. You may also not like the foul smell from such a place.

Step 5: Secure the Sink

Use stack boards to hold the undermount sink into position beneath the countertop. This stage is a bit tricky, but if you use the stack boards properly, it's not too difficult. Ensure the rims are well-aligned with the countertop's edges if installing a zero reveal style. If you want the lips revealed, ensure they rise over the countertop to the right height.

Then hold the sink to place by clamping it to the support and glue the studs. Use a reliable epoxy paste mixed with a hardener to stick the studs, which should not be over 25cm apart. Take silicone caulk and spread it around the countertop's cutout area. Ensure the caulk bed is over the sink's rim. Use a wingnut to tighten the studs and ensure no gaps between the countertop and sink. Then wipe out any caulk, glue, and dirt, and voila! You have replaced your undermount kitchen sink.


Replacing an undermount kitchen sink may be tricky, but if you use the above guide, it will be easy. Consider the type of countertop you're using while replacing your undermount kitchen sink for the best results. If you can't replace the tub yourself, seek assistance from a professional.