How to Replace a Bathroom Sink Cabinet | Step-By-Step Vanity Swap

Removing the Old Vanity

Work through these steps in order to save yourself a wet floor and scraped wall.

1. Shut off the water. Turn hot and cold shut-off valves under the sink clockwise. If missing, shut the main water supply.
2. Open the faucet to drain lines. Place a bucket under the P-trap. Loosen slip nuts with adjustable wrench and pull the trap off. That bucket is non-negotiable.
3. Disconnect supply lines at shut-off valves. Catch drips and set aside.
4. Run utility knife along caulk bead where vanity top and backsplash meet the wall—this prevents peeling drywall.
5. Remove screws inside cabinet near the top anchoring it to wall studs. Gently pry cabinet from wall with pry bar; have a helper for larger units.

The old vanity slides free with only cutoff valves and drain stub-out left.

Installing the New Cabinet

Check for straight walls and level floor before committing to position.

1. Measure and mark plumbing locations on the new vanity back. Use hole saw to cut openings for drain and supply lines.
2. Slide vanity into place, set level on countertop area. If floor is uneven, slide shims under base until bubble centers. An unlevel vanity causes water pooling and sagging doors.
3. Locate wall studs with stud finder. Drill pilot holes through vanity back into each stud, drive 3-inch screws. If a stud is misaligned, use wall anchors rated for the vanity’s loaded weight.
4. Install countertop and sink. Run silicone adhesive along cabinet’s top edge, lower countertop into place, press against backsplash.
5. Attach faucet and drain per faucet kit. Apply plumber’s putty or silicone to drain flange, insert into sink opening, tighten locknut from below.

The countertop sits level, cabinet is rock-solid against studs, faucet is mounted with no wobble.

Reconnecting the Plumbing and Testing

Test everything with water before declaring the job done. Tighten only until snug—plastic fittings crack easily if overtightened.

1. Reassemble P-trap by connecting sink tailpiece to wall drain stub-out. Hand-tighten slip nuts, then quarter-turn with channel-lock pliers.
2. Connect supply lines—hot to left valve, cold to right. Hand-tighten nuts at faucet and shut-off valves, then snug with wrench. No more than quarter-turn past hand-tight.
3. Apply silicone caulk where vanity and countertop meet wall. Smooth with wet finger, let cure per package (usually 24 hours).
4. Leak test: slowly open shut-off valves, run water for one minute, feel every joint with dry paper towel—supply lines, P-trap slip nuts, drain flange. Fill basin halfway, drain, watch P-trap. A dry towel means a good seal.