Sink Installation Guide: Vessel & Undermount Sinks

Set the vessel on the counter where it will live. Centre it on the cabinet, leave comfortable clearance from the backsplash, and mark the drain location on the counter with painter's tape and a pencil.

A vessel sink needs a tall “vessel” faucet or a wall-mounted faucet. The spout must clear the rim of the bowl and reach far enough over it that water lands in the basin, not on the counter. Confirm this before drilling anything.

If your counter is not pre-drilled, drill a 1¾" (45 mm) hole at the marked drain location. (Stone and quartz counters: have your fabricator do this.)

Set the vessel over the hole and check that it sits flat and stable. If your sink came with a mounting ring, place it under the base — it levels the vessel and protects both surfaces.

Run a bead of silicone around the underside of the vessel base (or on the mounting ring), set the sink in position, and press down gently. Wipe away any squeeze-out immediately with a damp cloth.

Vessel sinks require a vessel-style drain (grid drain or pop-up drain) with a long threaded tailpiece that passes through both the basin and the counter. Fit the drain from above, then tighten the lock nut from below — snug, but do not over-tighten: excessive force can crack ceramic, glass or stone vessels.

Connect the drain tailpiece to the P-trap (a bottle trap is a clean-looking option for open vanities), reconnect the water supply lines, and turn the water back on.

Run the water, fill and drain the basin, and check every joint underneath with a dry hand or tissue. Let the silicone cure for 24 hours before heavy use.

Every undermount sink ships with (or has available) a cutout template. It defines three reveal options:

• Positive reveal — The countertop edge stops short and a rim of the sink shows. Easiest to clean around the sink itself.
• Zero (flush) reveal — The countertop edge is flush with the sink wall. The cleanest look; requires a precise cut.
• Negative reveal — The countertop slightly overhangs the sink wall. Hides the silicone joint; the most common choice in kitchens.

Most kitchen installations use a zero or slight negative reveal. Stone and quartz cutouts should always be cut and polished by your countertop fabricator using the template.

Hold or clamp the sink under the cutout to confirm the fit. Install the faucet on the countertop first, and fit the garbage-disposal flange or strainer to the sink now — both are far easier before the sink is mounted.

Clean the underside of the countertop and the sink's mounting flange with denatured alcohol and let them dry. Apply a continuous, unbroken bead of 100% silicone around the top edge of the sink flange.

With a helper, lift the sink into position and press it firmly against the countertop. Support it from below (a simple 2×4 brace across the cabinet works) and fasten the undermount clips evenly around the perimeter, following the anchor positions on the template. Tighten gradually and evenly — over-tightening one clip can crack a stone countertop.

For large kitchen sinks, and any sink that will carry a garbage disposal, we recommend additional support rails or a sink support frame so the full weight is not carried by the clips and silicone alone.

Wipe off squeezed-out silicone immediately for a clean joint. Leave the sink supported and do not connect the plumbing or fill the sink for 24 hours while the silicone cures.

Connect the drain (and disposal, if fitted), the P-trap and the water supply lines. Fill the sink to the brim, let it stand for 15 minutes, then drain it while checking the rim joint and every plumbing connection for leaks.