How to Seal an Undermount Sink

a bathroom sink
What You'll Need
100% Silicone sealant
Denatured alcohol

Undermount sinks are a beautiful and modern additions to any kitchen or bathroom upgrade. Sealing an undermount sink is straightforward, and requires only a few simple steps.

Step 1 - Prepare the Countertop

If this is a new installation, start with the countertop turned upside down on a sturdy surface. Dry fit the sink and mark the placement. Clean the underside of the counter thoroughly with denatured alcohol. Even small amounts of dust or debris will compromise the sealant. If you are replacing the sealant on an existing undermount sink, remove the old sealant as carefully as possible to avoid scratching or damaging the fixture. Clean around the juncture of the counter and sink as much as you can, getting into as many of the tight spots as possible with the alcohol. Let the area air dry thoroughly.

Step 2 - Apply Sealant

Apply a steady bead of silicone around the edge of the countertop (if new install) or around the juncture between the counter and sink (if existing). Place the sink and clamp it into place. Allow the sealant to dry overnight before finishing the installation or using the sink.

Step 3 - Clean Up

Use a damp rag to clean up any oozing sealant or drips. Silicone will scrape away easily when dry.