How to Install a Bathroom Vanity

Turn off the hot and cold shut-off valves under the sink. Open the faucet to relieve pressure. Place a bucket under the P-trap and disconnect the supply lines from the shut-off valves. Loosen the slip nuts on the P-trap and remove it. Stuff a rag in the drain pipe to block sewer gas. Disconnect any pop-up drain linkage.

Remove any screws or brackets securing the vanity to the wall (check inside the cabinet along the back rail). Cut any caulk between the vanity top and the wall with a utility knife. Carefully pull the vanity away from the wall and remove it. If the vanity has a separate top, remove the top first (it may be siliconed or clipped to the base). Patch any wall damage behind the old vanity.

With the old vanity out, inspect the wall and floor. Repair any damaged drywall. If the new vanity is smaller than the old one, you may need to paint or patch the wall where it was previously covered. Check the floor for level — shim the new vanity if needed. Locate the wall studs with a stud finder and mark them with tape above where the vanity back rail will be.

Slide the new vanity into position. Check for level front-to-back and side-to-side. Use shims under the base to level it on an uneven floor. Mark the wall stud locations on the back rail of the vanity. The vanity must be level for the doors and drawers to function properly and for water to drain correctly.

Drive screws through the back rail of the vanity cabinet into the wall studs. Use at least two screws, one into each stud. The screws should be long enough to penetrate the stud by 1.5 inches. Don't overtighten — you can pull the back rail out of square. Trim any protruding shims flush with the base using a utility knife.

If the vanity top doesn't have the faucet pre-installed, mount the faucet now (it's easier before the top is in place). Apply plumber's putty around the drain flange and seat it through the sink hole. Connect the drain body and pop-up assembly from below. Follow the faucet manufacturer's instructions for supply line connections.

Apply a bead of silicone caulk along the top edge of the vanity base. Set the top in position, pressing it down evenly. Connect the supply lines to the shut-off valves (hand-tight plus a quarter turn with pliers). Install a new P-trap, connecting the tailpiece to the drain pipe in the wall. Make sure the P-trap slopes slightly downward toward the wall.

Apply a bead of silicone caulk where the vanity top meets the wall (backsplash joint). Smooth with a wet finger. Turn on the shut-off valves slowly and check every connection for leaks. Run water for a full minute and check the P-trap and supply connections. Tighten any dripping joints a quarter turn. Install the mirror, light fixture, and accessories.