How to Install a Bathroom Sink

hands installing bathroom sink plumbing
  • 1-4 hours
  • Intermediate
  • 0-500

There’s no reason to fear a bathroom sink installation. You’ve got this.

From framing it in to hooking it up, you’ll be washing your hands of your old sink and enjoying your new one in no time.

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Step 1 - Avoid Common Mistakes

Although it’s not an arduous task, there are myriad ways this project can go sideways. Knowing the obstacles in advance will help your bathroom sink installation go more smoothly.

First off, make sure you’re following all local building codes. That means paying fees for permits if necessary and having an inspector sign off on the project if mandated.

Understand what size plumbing you need so you don’t end up with pipes that are too small to handle the required drainage.

Also consider the type of plumbing you currently have compared to what you plan to use. For example, if you’re attaching copper to galvanized pipes, be sure to use a brass or dielectric fitting between the two.

Another common mistake is failing to use plumber's tape. The product is ubiquitous for a reason—it’ll save you from leaks and related damage.

Be sure to level your counter and sink as you work, and double check that you're leaving enough length when working with supply hoses.

When cutting the capped supply lines to install your shut-off valves, cut the 1/2" copper supply line at least 1 1/2-inches from the finished wall to allow for an escutcheon and shut-off valve compression nut and ring.

Also use caution when attaching valve, tubing, and hose fittings. Any misalignment can lead to expensive leaks.

Finally, when turning the water back on in your home, always run the outside hose valve or flush your toilets to bleed dirt and air from the lines.

This debris can cause problems in your sink faucets and other plumbing trim.

Step 2 - Rough in the Plumbing

plumber installing sink pipes

Assuming you’re working with completed household plumbing, you’ll be connecting into the pipes in the wall and/or floor.

Rough plumbing for a bathroom sink includes hot and cold supply connections and stub outs, shutoff valves, transition fittings, and possibly flexible tubing for above the shutoff valves.

Air chambers may also be required.

Step 3 - Remove Old Fixtures

For a bathroom sink replacement, turn off the water at the source. Then disconnect hoses or tubing and plumbing from beneath the existing sink.

Evaluate whether you can leave the faucet in place or if you need to remove it from the sink.

Release the sink from the caulking and remove it to another location. There may also be clips holding the sink into place.

Step 4 - Evaluate Framing

Depending on the type of sink you’re installing, you may need to frame in the space to support it.

Moving from a round to a square sink, for example, may require cutting out a portion of the countertop.

On the other hand, a vessel sink may not work with your current setup so you may need to replace the counter as part of your bathroom sink installation.

In addition to the actual support for the sink, ensure the clearance from the side of a bathroom sink to a toilet tank or finished wall is at least four inches.

Distance to an adjacent tub, however, may be as little as two inches. There must also be a minimum of 21 inches from the front edge to a wall or fixture to meet most building standards.

Step 5 - Install the New Faucet

If appropriate, install your new faucet, aligning it with the holes in the sink and attaching the hardware.

Step 6 - Place the Sink

hands installing bathroom sink

Depending on your system, the faucet may be installed after the sink placement instead of vice versa.

Place the sink into the space, applying caulking to the bottom of a drop-in sink and to the top of an undermount model.

This helps create a strong seal and eliminate leaks.

For a new installation, carefully cut pipes and tubing as needed, using a wheel cutter to avoid flattening soft pipes.

Slip on the escutcheon, the coupling nut, the compression ring, and the valve. Hold the valve outlet up and slide it over the compression ring.

Tighten down the coupling nut onto the valve using two crescent wrenches. It will usually squeak when it is properly seated.

Connect the drain pipes beneath the sink.

Step 7 - Restore Water and Check for Leaks

When water pressure is restored, run water into the basin and check for any leaks around and below the sink.

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