How to Install a Bathroom Vanity and Sink

Installing a bathroom vanity is the kind of project that looks daunting until you break it down into plumbing and carpentry—both of which are straightforward when you take them in order. The vanity anchors the whole bathroom; get this right and everything else follows. The project hinges on three things: making sure the new cabinet sits level and secure against the wall, running your supply and drain lines correctly so they don't leak, and ensuring you have the right rough-in measurements before you buy anything. This is absolutely doable for someone with basic tool skills and patience for methodical work. The key is preparation. Before you pick up a vanity, measure your space precisely, know where your existing plumbing comes out of the wall, and understand what size cabinet will fit your bathroom and your budget. Once that's done, the installation itself becomes a matter of careful sequencing: water off, old vanity out, new one in, sealed tight, plumbing connected, tested, and done.

1. Turn off water and drain the lines. Locate the shutoff valves under the sink—one for hot, one for cold—and turn them clockwise until snug. Turn on the faucet and let any remaining water drain out. If you can't locate the valves or they don't work, shut off water at the main supply line to the house.
2. Disconnect supply and drain lines. Place a bucket under the P-trap (the U-shaped pipe below the sink) and unscrew it by hand or with an adjustable wrench. Disconnect the hot and cold supply lines at the shutoff valves using an adjustable wrench, working slowly so water doesn't spray. Remove the old faucet if it comes with the vanity; otherwise leave it for now.
3. Remove the old vanity. Look for caulk or sealant around the top edges where the vanity meets the wall, and cut through it with a utility knife. Check inside the cabinet for any fasteners securing it to the wall studs, and remove those screws. Unscrew any brackets under the countertop. Gently pull the vanity away from the wall—it's heavy, so get help or slide it out in stages.
4. Prep the wall and position the new vanity. Clean off any old caulk, paint, or debris from the wall. Check the floor with a level—if it's uneven, shim under the vanity feet as you set it in place. Slide the new cabinet into position and use a level on top to check it's flat front-to-back and side-to-side. Mark the location of the wall studs with a pencil so you know where to screw into solid wood.
5. Secure the vanity to the wall. Drill pilot holes through the vanity's back rail into the wall studs, then drive 2½-inch wood screws through the rail into the studs. Use at least two screws, more if the cabinet is wider than 48 inches. Ensure the vanity doesn't rock or shift when you push on it.
6. Connect supply and drain lines. Reattach the P-trap to the drain stub coming out of the wall, hand-tightening first, then snugging with a wrench—tight enough to seal but not so hard you crack the fitting. Reattach the hot and cold supply lines to the shutoff valves. Hand-tighten first, then use a wrench for a final quarter-turn.
7. Test for leaks and seal the top. Turn the shutoff valves back on slowly. Turn on the faucet and let water run, watching under the vanity for any drips at the P-trap, supply lines, or shutoff connections. Turn off the faucet and check again in five minutes. Once you confirm no leaks, apply a continuous bead of caulk where the vanity top meets the wall to prevent water from seeping behind the cabinet.
8. Install the sink and faucet. If the sink didn't come pre-installed, set it into the countertop opening and secure it according to the manufacturer's instructions—some use mounting brackets underneath, others use adhesive or clips. If the faucet wasn't pre-installed, insert it through the mounting hole and tighten the supply lines to its shanks. Connect the drain tailpiece to the P-trap.