A bathroom vanity goes in cleanly by leveling the cabinet, anchoring to studs, setting the top, then connecting faucet, drain, and supply lines.
You can swap an old cabinet for a fresh unit in an afternoon with a steady plan. This guide lays out the sequence, the why behind each step, and the small checks that keep water where it belongs. Read straight through once, gather tools, then follow the steps in order. The payoff is a square box, a tight top, smooth doors, and dry plumbing.
Tools And Materials You’ll Use
Stage everything before you shut water off. A tidy setup saves trips while the trap is apart. Use this checklist and add brand-specific parts from your faucet and drain box.
| Item | Purpose | Pro Tip |
|---|---|---|
| Adjustable wrench, basin wrench | Tighten supply nuts and faucet mounts | Back up with a second wrench to avoid twisting valves |
| Drill/driver & bits | Pre-drill cabinet backs; drive mounting screws | Countersink to prevent plywood blowout |
| Stud finder & level | Locate studs; keep the box plumb | Confirm with a tiny nail test hole |
| Shims | Take out floor dips and wall bows | Trim flush after anchoring |
| Hole saws/jigsaw | Cut for drain and supplies | Tape the cut line for cleaner edges |
| Silicone sealant | Seal splash zones and the top | Pick a mildew-resistant bathroom grade |
| Plumber’s putty | Seal many metal drains | Skip putty on stain-prone stone; use silicone |
| P-trap kit (1¼ or 1½ in.) | Connect sink tailpiece to wall drain | Dry-fit first; align the trap arm level to the wall stub |
| Supply lines (3/8 in. comp.) | Feed hot and cold to the faucet | Buy lines with integrated gaskets; no tape needed |
| Painter’s tape & caulk tool | Cleaner joints and crisp edges | Peel tape while the bead is still wet |
| Safety glasses & gloves | Protect eyes and hands | Kill power to nearby outlets if cutting close |
Plan The Swap
Pick The Right Size And Layout
Measure wall length, door swing, and the centerline of the existing drain. Match the cabinet width to the room, then check drawer paths against the stops. Wall-hung units need solid blocking; freestanding boxes spread load through the base and shims.
Check Rough Heights
Note the height of the drain stub-out and the hot/cold valves. A low stub pushes the trap down; a high stub crowds the tailpiece. If the rough is far off, pause and call a licensed pro for rework before you mount a cabinet you can’t plumb neatly.
Remove The Old Unit Cleanly
Shut the angle stops. Open the faucet to bleed pressure. Place a bucket under the trap and loosen slip nuts. Pop the top free of caulk with a sharp knife. Back out the rail screws, slide the box forward, and cap the valves to avoid bumps while you work.
Prep The Space
Wall And Floor Checks
Lay a straightedge along the wall to spot bows. Sweep the floor area and pull any proud nails or staples. If the wall is out more than a pencil width, plan to scribe the cabinet back for a tight fit.
Find Studs And Plan Fasteners
Mark stud centers across the install span. If only one stud lines up with the back rail, add two heavy-duty toggles through the rail for extra bite, but always land at least one rail screw into solid framing.
Dry-Fit The Box
Set the cabinet in place with a thin spacer off a side wall if needed. Open doors and drawers to confirm handles clear trim and the door casing. Mark the cabinet top line on the wall for later caulk alignment.
Bathroom Vanity Installation Steps: Start To Finish
1) Level And Shim
Place a long level across the cabinet and along the face. Shim front corners and low spots until the bubble centers both ways. A level box makes doors hang square and keeps the sink drain centered in the trap.
2) Anchor To The Wall
Pre-drill through the back rail at stud marks. Drive cabinet screws until snug without crushing the panel. Recheck level, then trim shims flush with a sharp blade. If the box has a separate toe kick, set and fasten it first so the carcass sits solid.
3) Cut Clean Openings
Mark the drain and valve locations on the cabinet back using the stub-outs as a guide. Drill a pilot, then switch to a hole saw or jigsaw. Keep cuts neat; ragged edges splinter and make later service fussy.
4) Set The Top
Dry-fit the countertop. For a drop-in sink or an integrated top, run a thin continuous bead of silicone along the rim and at the backsplash line. Lower the top, press lightly, and wipe squeeze-out. Carry stone flat and use a helper to avoid cracks.
5) Mount Faucet And Drain
Assemble the faucet per the brand sheet. Many drains seal with plumber’s putty; some specify silicone on stone or composite. Form a neat rope of putty, seat the flange, and snug the locknut evenly. Set the pop-up, align the rod, and tighten hardware just to firm.
6) Build The P-Trap
Slide the tailpiece into the drain body. Dry-fit the trap with slip nuts and beveled washers facing the correct way. Keep the trap arm nearly level into the wall; a sag invites slow flow. Hand-tighten, then give a small wrench nudge if a seam weeps during testing.
7) Connect Supply Lines
Attach braided lines to the faucet first, then to the stops. Snug only until resistance rises; crushing gaskets creates drips. Choosing a faucet with the WaterSense mark saves water while keeping a crisp stream; see the WaterSense faucet spec for flow guidance across common pressures.
8) Seal The Perimeter
Mask the wall and top. Run a smooth silicone bead along splash points and at cabinet-to-wall seams. Tool the joint for full contact, then pull tape while the bead is still wet for a clean line.
9) Restore Water And Test
Open the valves and remove the aerator. Run water to purge air and debris, then check every joint with a dry tissue. A faint line on the tissue means a weep; snug that nut a quarter turn. Reinstall the aerator and wipe the cabinet dry.
Smart Details That Prevent Callbacks
Trap, Vent, And Slope
The trap sits below the sink outlet, holds a water seal, and ties to a vent so that seal doesn’t siphon. Where a mechanical vent is allowed, keep it above the flood rim and reachable. The ICC AAV guidance lays out clear heights and access notes for typical vanity setups.
Stops And Hoses
Old multi-turn stops stick and can leak after cycling. Swap to quarter-turn valves during a remodel. Hand-start every thread to avoid cross-threading. If a compression ferrule spins, replace it rather than cranking harder.
Seal Choices Around The Drain
Putty stays pliable and lifts clean during later service. Silicone bonds and needs cutting to remove. Check your top material and the drain body sheet before you pick a sealant, and wipe excess neatly so the flange seats flat.
Common Measurements And Clearances
These ranges help plan rough heights and clearances for powder rooms and full baths. Always match the layout to local rules and the brand sheets that ship with your fixtures.
| Part | Typical Range | Notes |
|---|---|---|
| Cabinet height | 32–36 in. | Comfort-height tops land near 34–35 in. |
| Drain stub-out | 18–21 in. off floor | Center on the sink; keep square to wall |
| Supply stub-outs | 20–24 in. off floor | 12–16 in. apart left/right |
| Trap arm slope | About ¼ in. per foot | Keep a level look inside the cabinet |
| Side clearance | ≥1 in. from walls | Leaves room for caulk and splash |
| GFCI outlet | Near the mirror zone | Location set by local electrical rules |
Wall-Hung Units And Small Baths
Blocking And Mount Rails
Floating boxes need solid backing. If you opened the wall for rough work, add a continuous 2× ledger across the span, then lag the rail into that ledger. Check plumb and level twice; a tilt shows fast under a mirror.
Traps And Space
Short P-traps and slim bottle traps free inches in tight bases. Use only listed parts for sink drains and keep slip-joint access clear so service stays easy later.
Troubleshooting Leaks And Fit Issues
Slow Drains Or Gurgles
Look for a sagging trap arm, a missing washer, or a blocked vent. A stuck AAV will pull air through the trap and make noise; replace the device if the cap no longer moves freely.
Persistent Weeps At Slip Joints
Check that beveled washers face the right way and that cut ends are square. Over-tightening can distort plastic and worsen the drip. A fresh washer often ends it.
Misaligned Top Or Gaps
Recheck level and wall flatness. Add or shave shims, relax the rail screws, nudge the box, then retighten. Fill small wall seams with a neat silicone line; large gaps call for scribing or a filler strip.
Drawer Hits A Valve
Switch to compact quarter-turn stops or add a 90-degree outlet stop to redirect hoses. A shallow trap can gain an inch of room without odd angles.
Care And Maintenance After Day One
Check the trap and supply nuts a day later. Materials settle with heat cycles. Keep a towel in the base for week one as an early leak alert. Clean silicone with a mild bathroom cleaner and a soft cloth only. Wipe standing water quickly so wood edges don’t swell.
Safety Notes And Clean Work Habits
Protect Finishes
Cardboard under the cabinet prevents scratches while you shift and shim. Tape faucets before you swing a wrench near the spout to avoid nicks. Set metal tools on a towel, not on the top.
Mind Power And Sharp Tools
Cut with both hands on the saw and eye protection on your face. If a receptacle sits inside the base, flip that breaker while you cut the cabinet back. Clear chips often; heat builds up and melts edges during long hole-saw passes.
Budget, Timing, And Disposal
A basic swap with no rough changes lands in the half-day range. Add time for wall patches, valve swaps, or tile scribing. Keep a few extra shims, slip-joint washers, and a spare supply line on hand; small parts save long store runs. Remove the old unit in one piece if a reuse is planned, or break it down to fit curbside rules where you live.
Printable Walkaway Checklist
Run this quick list before you call it done: cabinet sits level and tight to the wall; doors and drawers clear; faucet mounts are firm; drain holds water, then releases cleanly; supply lines show no moisture; bead lines look smooth; caulk cures per label; aerator runs clear; shutoffs open and close with two fingers; you saved the brand sheets in the base for future service.
Why These Choices Work
Water-saving faucets with the WaterSense mark prove out flow and feel across pressure ranges, and that cuts waste without turning hand-washing into a chore. Venting that stays reachable keeps service simple. Trap slope and short, square runs reduce clog risk. Careful sealing stops water from sneaking under the top, which keeps the base free of swelling and odors. The steps above balance a clean look with parts you can service later without tearing into finished walls.