What You Need to Know Before Starting
Replacing a bathroom vanity is a project you can do yourself if you have basic plumbing knowledge and the right tools. The job breaks into three main parts: turning off the water and disconnecting the old vanity, removing it from the wall, and installing the new one. Most people finish in four to six hours, though the timeline depends on how stuck your old vanity is and whether you run into unexpected plumbing or wall damage.
Before you buy a new vanity, measure the space where the old one sits. Write down the width, depth, and height. Check how far the water supply lines and drain are from the wall and floor—your new vanity's plumbing holes need to line up, or you'll have to reroute pipes. If you're replacing the countertop and sink too, buy them as a unit or measure the sink opening on your new vanity so the countertop fits.
Key Takeaways
- Turn off the water at the shutoff valve under the sink before you disconnect anything, and have a bucket ready to catch water that remains in the pipes.
- Disconnect the supply lines, drain, and any caulk holding the vanity to the wall before you try to pull it out.
- Check the wall behind the vanity for damage or mold before you install the new one, and patch or treat it if needed.
- find the new vanity to the wall studs with screws, not just caulk, so it doesn't shift or pull away over time.
- Reconnect the supply lines hand-tight first, then use a wrench to tighten them a quarter turn more—over-tightening cracks fittings.
Gather Your Tools and Materials
You'll need an adjustable wrench, a screwdriver set, a utility knife, a level, a drill with bits, and a bucket to catch water. Have towels or a small tarp ready to protect your floor. If the vanity is caulked to the wall, a caulk removal tool or old putty knife speeds up the job.
For the new vanity, you'll need shims (thin wedges to level it), wood screws that fit your wall studs, and plumber's putty or silicone caulk. If you're replacing supply lines, buy new ones rated for your water pressure—usually 3/8-inch compression fittings. If the drain doesn't match your new vanity's opening, you may need a new P-trap or tailpiece, which are inexpensive and sold at any hardware store.
Turn Off Water and Disconnect the Old Vanity
Locate the shutoff valve under the sink—it's a small knob on the water line coming from the wall. Turn it clockwise until it stops. Turn on the faucet to release pressure and drain any water left in the lines. Place a bucket under the supply lines where they connect to the faucet, then use your wrench to loosen the nuts holding them. Water will drip out, so let it collect in the bucket.
Next, disconnect the drain. Look under the sink at the P-trap—the curved pipe below the drain opening. Loosen the large nuts on both ends of the P-trap by hand or with a wrench, then slide it out. If caulk seals the vanity to the wall, run your utility knife along the edge to cut it. You may need to do this on all four sides. Once the caulk is cut, try to pull the vanity away from the wall. If it's screwed to the wall studs, remove those screws first—they're usually hidden behind the countertop or inside the cabinet.
Remove the Old Vanity and Inspect the Wall
With the plumbing disconnected and fasteners removed, pull the vanity straight out from the wall. You may need help if it's heavy or wedged tight. Once it's out, look at the wall behind it. Check for water stains, soft spots, or mold—these mean the wall has absorbed water and may need to dry out or be replaced before you install the new vanity.
If you see minor stains but the wall is solid, let it air dry for a few hours. If there's mold or soft drywall, cut out the damaged section with your utility knife and patch it with new drywall and joint compound, or call a professional. This step prevents mold from spreading under your new vanity. Also check the floor for damage. If the subfloor is soft or rotted, it needs repair before you set the new vanity on it.
Position and Level the New Vanity
Slide the new vanity into place and check that the water supply and drain openings line up with your existing pipes. If they don't line up exactly, you have two options: adjust the vanity position slightly, or reroute the pipes. Small adjustments are easier—move the vanity left or right a few inches if possible. If the pipes are too far off, you may need to hire a plumber to relocate them, which adds cost and time.
Once the vanity is positioned, place your level on top and check that it's straight front to back and side to side. If it tilts, slide shims under the feet until it's level. Shims are thin wooden wedges—tap them in gently with a hammer until the vanity sits flat. This is important because a tilted vanity stresses the plumbing connections and makes drawers or doors hang unevenly.
find the Vanity to the Wall
Locate the wall studs behind the vanity using a stud finder, or tap the wall with your knuckles—studs sound solid, hollow spots are between them. Mark the stud locations on the back of the vanity or the wall. Drill pilot holes through the vanity back into the studs, then drive wood screws through the vanity into the studs. Use at least two screws, spaced a few inches apart. These screws hold the vanity in place and prevent it from pulling away from the wall when you open drawers or lean on the countertop.
Do not rely on caulk alone to hold the vanity—caulk is a seal, not a fastener. After the screws are in, run a bead of silicone caulk along the top edge where the vanity meets the wall. This keeps water from running behind the vanity and damaging the wall.
Reconnect the Plumbing
Reconnect the P-trap first. Slide it back under the drain opening and hand-tighten the nuts on both ends. Once hand-tight, use your wrench to turn each nut a quarter turn more. Do not over-tighten—you'll crack the plastic fitting. The connection should be snug but not forced.
Next, reconnect the supply lines. Hand-tighten the nuts where they connect to the faucet, then use your wrench to turn each one a quarter turn more. Turn the shutoff valve back on by turning it counterclockwise. Check all three connections—both supply lines and the drain—for drips. If water leaks, turn off the valve, tighten the fitting a quarter turn more, and check again. Let the water run for a minute to flush out any debris from the old pipes, then check once more for leaks.
Frequently Asked Questions
What if the water shutoff valve under my sink doesn't work?
If the valve won't turn or water keeps running, locate the main shutoff for your house—usually in the basement, crawlspace, or outside near the foundation. Turn that off instead. After you finish the vanity, have a plumber replace the broken shutoff valve so you can isolate the bathroom sink in the future.
Can I install a vanity that's wider or narrower than the old one?
Yes, as long as the water supply and drain lines can reach it. If the new vanity is narrower, the pipes may stick out visibly on the sides—you can hide them with trim or a decorative panel. If it's wider, make sure the pipes reach the new openings without stretching or kinking. Measure twice before you buy.
Do I need to turn off water if I'm only replacing the vanity, not the faucet?
Yes. Even if you're keeping the faucet, you still disconnect the supply lines to remove the old vanity. Turning off the water prevents spraying and makes the job cleaner and safer.
What should I do if I find mold behind the vanity?
Small surface mold can be cleaned with a bleach solution and allowed to dry. If mold covers a large area or the drywall is soft, cut out the affected section and replace it with new drywall. Mold grows in damp spaces, so make sure your bathroom has good ventilation—run the exhaust fan during and after showers.
How long does it take for caulk to dry before I can use the sink?
Silicone caulk typically dries in 24 hours, though you can use the sink after a few hours if you're careful not to splash water on the fresh caulk. Check the label on your caulk tube for the exact drying time, as it varies by brand and temperature.