How to Replace a Bathroom Vanity

Replacing a bathroom vanity is one of those projects that looks more complicated than it actually is—and the payoff is immediate. A new vanity transforms the entire feel of a bathroom without requiring structural work or permits. The key is taking time on the front end to measure, shut off water properly, and disconnect everything methodically. Done well, you'll have a functional, fresh-looking sink setup that handles daily use for years. The work itself is mostly disconnecting, moving things aside, and reassembling—no special skills required, just patience and a willingness to get under the cabinet with a wrench.

1. Test the Shutoff Valve First. Locate the water shutoff valve behind the vanity, usually two chrome knobs (hot and cold) mounted on the supply lines coming from the wall. Turn both clockwise. Open the faucet above to confirm water stops flowing. If water still runs, you'll need to shut off the main water supply for the house and have the valve serviced later. Close the faucet once you've confirmed the shutoff works.
2. Clear the Cabinet Space. Open the vanity doors and remove everything inside—toiletries, cleaning supplies, the works. Locate the pop-up drain stopper mechanism under the sink (usually a rod connected to the back of the drain pipe). Lift the stopper lever up, then rotate the mechanism counterclockwise to disconnect it from the drain assembly. Wipe out any standing water or debris from the cabinet floor.
3. Remove the P-Trap. Look under the sink at the curved trap pipe directly below the drain. Using a pipe wrench or adjustable wrench, loosen the large coupling nut where the trap connects to the wall drain (usually pointing horizontally into the wall). Loosen the nuts on both ends of the trap and slide it out carefully. If there's standing water in the trap, place a small bucket underneath to catch it. You may have 1–2 cups of water, so don't rush this step.
4. Disconnect the Supply Lines. Using a wrench, loosen the coupling nut where each supply line (hot and cold) connects to the shutoff valve behind the wall. Turn counterclockwise until hand-tight, then use the wrench for the final quarter turn. Have a small towel ready to catch any remaining water in the lines. Gently pull the supply lines away from the shutoff valves and set them aside.
5. Extract the Old Vanity. Reach up behind and underneath the vanity where it meets the wall studs. Most vanities are secured with 2–4 bolts driven through the back or top frame into the wall. Use a wrench or socket set to loosen and remove these bolts completely. If the vanity feels caulked to the wall, run a utility knife along the seam to break the seal. With a helper, carefully pull the old vanity away from the wall and set it on its side to inspect the back. You may see old caulk residue or drywall damage—note it for later repair.
6. Clean and Repair the Wall. With the old vanity removed, inspect the wall and floor where it sat. Remove any remaining caulk with a putty knife and clean away dust and debris. Look for drywall damage, water stains, or soft spots. If the drywall is wet or soft, cut out the damaged area with a utility knife and patch it with new drywall and joint compound—allow it to dry fully before proceeding. Check that the floor is level using a 2-foot level. Minor slopes are normal; major ones mean the floor may need shimming when the new vanity goes in.
7. Level the New Vanity. Carefully slide the new vanity into place. Check that the countertop sits level from front to back and side to side using a 2-foot level. If the floor isn't perfectly level, place shims (plastic or wood) under the vanity feet or base to bring it into level. You may need one shim under one corner and none under others. Ensure the vanity sits flush against the wall—no gaps. The goal is a vanity that looks straight and sits evenly on all legs.
8. Bolt to the Wall. Once the vanity is level and positioned, locate the mounting holes on the back frame (usually 2–4 pre-drilled holes). Align these with the wall studs—use a stud finder to confirm you're hitting solid wood. Drill pilot holes through the vanity frame into the wall studs, then install lag bolts or wood screws rated for your wall type (drywall anchors if no studs are present, though studs are preferable). Tighten bolts snugly but don't over-torque; you want the vanity secure but not crushing the frame.
9. Reconnect the Trap. Slide the P-trap back into position beneath the sink drain. Hand-tighten the coupling nuts first—one at the drain outlet above, one at the wall drain below. Use a pipe wrench to snug each nut an additional quarter turn. The goal is hand-tight-plus-a-quarter, not maximum force. Water should not drip from these connections when the sink is full. If it does, tighten slightly more.
10. Restore Water and Test. Attach the hot supply line to the hot shutoff valve and the cold supply line to the cold valve. Hand-tighten the coupling nuts, then use a wrench for a quarter-turn tightening. Turn the shutoff valves counterclockwise to restore water pressure. Open the faucet fully (both hot and cold) and let water run for 10–15 seconds to flush out air and sediment. Check both shutoff connections and the P-trap for drips. If you see water pooling, tighten the appropriate connection slightly more.
11. Reinstall the Stopper. If your new vanity uses the same drain assembly as the old one (check the drain opening size), reconnect the pop-up stopper rod. Slide the rod back into the mechanism at the back of the drain, aligning the pivot rod so the stopper rises and falls smoothly when you lift and lower the handle. If the new vanity has a different drain design or if the old mechanism is damaged, you may need a new pop-up assembly (most hardware stores stock universal kits for around $15). Test the stopper by opening and closing it several times—it should move freely without binding.
12. Seal the Gap. Run a continuous bead of 100% silicone caulk along the seam where the vanity back meets the wall. Use a caulk gun and maintain steady, even pressure. Smooth the caulk with a wet finger or caulk tool—don't leave it bumpy or uneven. Caulk prevents water from running behind the vanity and keeps dust out. Avoid getting caulk on the vanity finish or wall paint; wipe excess immediately with a damp cloth. Allow the caulk to cure per the manufacturer's instructions (usually 24 hours) before exposing the area to moisture.