An undermount sink, is a type of sink that is named because of its installation method. It is installed and secured underneath the countertop surface. Whereas, an inset sink is dropped into the pre-cut hole in the counter top and held in place by a lip that extends over the countertop surface. The main benefit to an undermount sink is that there is nothing in the way of the countertop surface and the sink bowl, so, any dirt or crumbs you would want to sweep into the sink will fall in easily and will not be caught on the lip of the sink.
Because the installation method makes the sink appear more permanent, people often ask “Can an Undermount Sink be Replaced?” The short answer is, Yes. Undermount sinks are removed by stripping the adhesive sealant and unbolting any braces holding the sink in place.
However, the level of difficulty when it comes to replacing or installing undermount sinks largely depends on whether you have a solid surface countertop (Granite, Marble, Quartz) or a laminate countertop.
Undermount sinks installed in a solid surface countertop are installed and adhered directly to the underside of the stone. Whereas, undermount sinks in a laminate countertop are adhered to the wood deck underneath the laminate covering (usually plywood) and the laminate is adhered over the sink. Therefore, if you have a laminate countertop and you want to replace or install an undermount sink, you will likely have to replace the entire laminate surface of your countertop.
Here is a super helpful video outlining the process of installing an undermount sink in a laminate countertop.
The remainder of this How-To article will relate to replacing an undermount sink in a solid surface, or stone, countertop.
Replacing Your Undermount Sink
If you decide that you do wish to replace your existing undermount sink, there are few simple steps that have been outlined in the remainder of this post.
Tools You Will Need
- A pair of pliers
- A razor or exacto knife
- A razor scraper or naked razor blade
- Denatured alcohol and a cleaning rag
- A Phillips head screw driver
- A bar clamp (Optional)
- 100% silicone sealant
Selecting Your New Sink
Once you’ve decided on the style and color of the new sink you want to purchase, you will want to make sure to measure the existing sink set up and get an idea for the dimensions. Measure the width, length and depth of your existing sink.
A new sink can be slightly deeper than the previous sink but you will need to make sure that the width and length of the new sink will fit with the existing hole cut in your stone countertop.
Most kitchen sinks come in three standard sizes; 24″, 30″, and 33″. These measurements measure the width (the longest side) of the sink bowl or bowls. The most commonly used kitchen sink size is 30″ which will fit most kitchens in any style of home.
There really is no standard size for a bathroom sink largely because the shapes of bathroom sinks vary a lot more than kitchen sinks. However, most round bathroom sinks are roughly 16 to 20″ in diameter, and most rectangular bathroom sinks are 19 to 24″ inches wide.
As a general rule of thumb the counter top you are installing the sink into needs to have at least an inch and a half of clearance on either side of the sink in order for the lip of the sink to attach properly. In other words, if you have 30″ sink you need a countertop that is at least 33″ inches wide. In most cases, this is only an issue with a smaller fixture you would find with a wet bar or a smaller bathroom.
Removing Your Existing Sink
Before you begin removing the sink, make sure the water supply to the faucet is turned off via the knobs in the cabinet below the sink, then disconnect the P-Trap arm (The white or black PVC pipe connected to the bottom of your sink) you should be able to unscrew this with your hand, if not, use a set of pliers. Additionally, unplug the garbage disposal if you have one and unscrew the fasteners to remove it from the bottom of the sink drain.
Generally, an undermount sink has two points of connection to the underside of the counter. The rim of the sink is glued to the underside of the counter with a silicone adhesive, or sealant. This is what holds the sink in place in relation to the hole in the counter and is the main method of connection.
As a back up to the adhesive, there are typically two metal clips bolted to the underside of the counter to further secure the sink in place.
To begin removing the existing sink, take your razor knife and begin slicing through the existing sealant holding the sink in place. The sealant is located in the small gap between edge of the countertop around the sink and the sink itself. Work your way around the sink slowly and apply steady pressure to ensure you cut as deeply through the sealant as possible.
After cutting through the sealant, unscrew the metal clips underneath the countertop. These are the last points of connection holding the sink in place so be sure when under the sink, to have someone else physically hold the sink in place to avoid it falling on the person unscrewing the clips.
After the sealant has been cut through and the clips have been removed, the sink should be able to slide out through the bottom of the cabinet.
Here is a super helpful video outlining this whole process and is the video I used when I replaced my sink.
Installing Your New Sink
Before installing the new sink into position, use a razor scraper to scrape off any residual sealant that was left on the underside of the counter from the old sink.
Then, use some denatured alcohol on a clean wash rag to wipe down the area where the old sink sealant was and the rim of the new sink to completely rid the surfaces of any small debris that may get trapped in the new sealant during installation.
Once the counter and new sink have been cleaned, place the new sink into the cabinet directly below the hole where the sink will be installed. Using a 100% silicone sealant, place a continuous bead of the sealant around the rim of the new sink.
Carefully lift the sink into position and hold it there while the sealant begins to take hold and adhere to the counter. To make sure the sink stays in position, either have someone hold the sink through the open drain hole, or use a bar clamp clamped to a 2×4 piece ran across the counter top and another 2×4 piece underneath the sink.
Now secure the metal clips that came with the new sink to the underside of the counter and your new sink will be fully secured into place. Now run a damp rag along the inside edge of the sink between the countertop to wipe away any excess sealant.
Allow 24 hours for the silicone sealant to fully dry before you set in the drain and reattach the P-Trap arm and the garbage disposal.
After the piping and garbage disposal have been reconnected, turn your water supply back on and enjoy your new sink!
