How to Replace a 4 Inch Bathroom Faucet? | Step-By-Step Swap

The job looks harder than it is. If your sink has three holes spaced 4 inches apart center-to-center, a standard 4-inch centerset faucet drops right in. Whether you’re fixing a leak or updating the look, the swap follows the same sequence: shut off the water, pull the old unit, seat the new one, and reconnect the supply lines.

What You Need Before You Start

Check that your sink has three holes at 4-inch center-to-center spacing. This pattern matches a standard 4-inch centerset faucet, where the spout and handles sit on one base plate.

Gather these tools:

• Basin wrench or adjustable wrench for the mounting nuts below the sink
• Plumber’s putty or silicone caulk if the new faucet lacks a gasket
• Bucket and towel for residual water
• Safety glasses

If you are unsure about any step, consult a qualified plumber rather than forcing a connection.

Removing the Old Faucet

Start by shutting off the hot and cold water. If under-sink shutoff valves are missing or unreliable, close the main supply instead. Then open the faucet handle to relieve pressure in the lines—a step that prevents a spray of trapped water when you disconnect things.

Work through this removal order:

1. Disconnect the hot and cold supply lines from the faucet tails.
2. Loosen the mounting nuts from below the sink with your basin wrench.
3. Lift the old faucet straight up and out of the deck holes.
4. Scrape away old putty, caulk, or residue from the sink surface so the new base seats flat.

Installing the New 4-Inch Centerset Faucet

Place the new faucet through the deck holes. If it comes with a gasket, set that in position first, then align the unit and tighten the mounting nuts from below. No gasket? Run a bead of plumber’s putty or silicone around the base opening before seating the faucet.

Follow this sequence for a clean install:

1. Drop the faucet through the holes and press it evenly against the sink deck.
2. Tighten the mounting nuts clockwise from underneath—snug and hand-tight, not cranked down.
3. Reconnect the hot supply to the hot inlet and the cold supply to the cold inlet. The lines and inlets are labeled separately; reversing them means your left handle controls hot water on the right side.
4. Turn the water back on slowly and open the handle to clear air from the lines.

Do not overtighten—official instructions repeatedly stress snug fits over force.

Once water flows, remove the aerator from the spout and run the water briefly. This flush step clears solder flakes or debris from the new lines before you reinstall the aerator.

If you are shopping for a replacement before starting, our roundup of top-rated models can narrow the choice: the best 4-inch bathroom faucet picks cover finishes, handle styles, and reliable brands worth comparing.

Common Mistakes That Cause Leaks

Most post-install leaks trace back to four avoidable errors:

• Overtightening. Snug mounting nuts and supply connections seat fine; extra force strips threads or cracks washers.
• Skipping the flush. Debris trapped behind a new aerator causes weak or sputtering flow.
• Wrong faucet type. A 4-inch centerset only fits sinks with 4-inch hole spacing; an 8-inch spread model leaves gaps.
• Rushing the leak check. Inspect every joint—supply lines, base, and handle connections—after turning the water back on.

Test each connection by running both hot and cold water for a minute, then feel under the sink for moisture.