How to Install Double Sink Bathroom Vanity | Step-By-Step

Installing a double sink bathroom vanity takes planning, plumbing work, and most of a weekend to complete.

For the full breakdown, see our best 48 Inch Double Sink Bathroom Vanity guide.

If you’ve bought a double-sink unit for a bathroom remodel, the job ahead is straightforward but unforgiving of shortcuts. The standard sequence runs from shutting off water to leak-testing every connection — and most mistakes happen before a single pipe gets cut. Measure the opening first, confirm the wall can support the cabinet, and dry-fit everything before you make any holes. This guide covers the full install from start to finish.

Measure and Prep the Space

Before buying or moving anything, measure the bathroom opening against the vanity’s dimensions. Double-sink vanities typically run about 60 inches wide, and the layout should have about 48 inches of front clearance so you can actually use both sinks. Confirm the wall width, depth, and height will all fit.

With the vanity confirmed to fit, shut off the water supply and open the faucet to relieve pressure. Disconnect the supply lines and remove the P-trap before cutting the backsplash caulk and pulling the old vanity out. This Old House’s guide for adding a second sink to a bath vanity goes through this teardown in detail.

Position, Level, and Anchor the Cabinet

Run a stud finder across the wall behind the vanity rough-in and mark every stud you intend to anchor into. Set the new cabinet in place, level it front-to-back and side-to-side, and use shims under the base where the floor is uneven.

Fasten the cabinet to the wall studs with screws when possible. If the holes don’t line up with studs, use the correct wall anchors rated for the cabinet’s loaded weight instead of driving screws into drywall alone. A double vanity filled with plumbing and countertop needs real support — mounting it to weak backing is one of the most common failure points.

Once the cabinet is level and anchored, dry-fit the top and mark the drain and supply pipe openings. Cut holes only after everything is marked and re-check the level once more before final fastening.

Hook Up Plumbing and Faucets

Confirm both sinks have even spacing and usable workspace around them before securing anything.

Connect the PVC drainpipes to both sinks, apply plumber’s tape to threaded fittings, and use pipe-joint compound on flexible water-supply-line threads. Reconnect the faucet and supply lines, then run water to both sinks and check for leaks at every joint. Also verify both sinks drain properly before you move on.

Seal and Finish

Seal the backsplash-to-wall joint with silicone caulk as well, since that seam is constantly exposed to water splashes.

If the plumbing rough-in doesn’t align cleanly with the new cabinet openings — a common issue when converting from a single sink — wall anchors may be needed for a more secure install. The Lowe’s vanity installation guide notes this same compatibility caveat. Test both sinks for drainage and leaks thoroughly before calling the job complete. Water and drain connections should be leak-tested before installation is considered done.

Common Mistakes to Avoid

• Not measuring the wall, plumbing rough-in, and clearances before buying the vanity.
• Skipping the dry fit and cutting pipe holes too early.
• Mounting to weak backing instead of studs or proper reinforcement.
• Failing to level the cabinet before fastening it.
• Forgetting to caulk the backsplash/wall seam and other water-exposed joints.
• Not testing both sinks for drainage and leaks after hookup.