How to Install Bathroom Vanity Plumbing Both Wall & Floor

Getting ready and getting dressed becomes so much easier plus convenient to do right after a shower if you have a bathroom vanity. So installing one inside your bathroom is definitely a step towards self appreciation.

During the bathroom vanity installation phase, one thing that some people find confusing to do is how to install bathroom vanity plumbing.

Some don’t bother and get a person hired for doing the chore. But if you wish to save that money and try things for yourself, we’ll share with you how to install bathroom vanity plumbing both wall floor.

Installing Bathroom Vanity Plumbing (Wall)

Step 1: Sink and Water Line Disconnection

The start of plumbing for bathroom vanity sinks will require you to disconnect the sink. Turn the water valves off or shutoff valve and release the existing plumbing or faucet pressure. 

The P-trap, a curved section should be getting a drain pipe right beneath the sink. You want to place a bucket or towel below it. So that any spilling water from the trap gets into it. Get the trap off from the drainpipe by loosening the top located nut. Get it out completely.

The valves should be disconnected from the supply line too. The sink backsplash connecting with the wall also needs to go off. Use a utility knife to cut the connecting sealant or caulk.

Step 2: Vanity Removal and Marking

Get the screws out from the wall that holds vanity in place. Carefully get the old bathroom vanity out too. There can be damage on walls that you should repair or repaint at this point. A putty knife or a simple brush for painting can help with any touch-up required.

Now the position of your new vanity needs some marking on the wall. You want to carefully mark the width and height. Make sure to mark the studs that are within vanity outside.

A stud finder can help you here. You may need to measure the pipe positions on the wall plumbing too. Especially when the new vanity has a solid back. Simply transfer all the vanity back measurements on the wall. Use the proper measurement hole saw for cutting pipe holes.

Step 3: Vanity and Top Installation

You want to slide the cabinet of vanity in position while making sure it’s lining with earlier marks. Get the doors of vanity out for easy installation. Check level and if there’s a need then adjust the height using shims.

Then drill the pilot holes on the closest studs. Use some screws to attach here. Use wall anchors if there are no studs, of course, the correct ones.

Step 4: Vanity with no countertop

Some vanity comes with no attached counter. In that case, you want to fix the top of the vanity with a cabinet using a thin bead of caulk. Reinstall the doors of vanity at this point.

The space between backsplash and wall, you want to put caulk beads here. Do this along the edge of the backsplash, where it is supposed to meet the wall.

Between the wall and vanity, you need to push caulk in this gap. Use a caulk finishing tool to do this. Or you can also use a nitrile gloved finger for this. Make sure to dip the finger in water first. There are the ones made with rubber too.

Step 5: Faucet Installation and Plumbing

At this point, you will be installing a bathroom sink drain. Learning the proper way on how to plumb a bathroom vanity sink drain is the key here. But before that, you need to also get the faucet inside.

Precisely follow the manufacturer-provided guidelines to do this. Also, consider sink compatibility as well as valve type for buying the faucet. It should fit with proper style and finish.

Right below the sink drain ring, you want to apply a plumber’s putty rope. 

Now with the new bathroom sink drain assembly line carefully connect P-trap. Following a clockwise direction, apply the plumbers’ tape. Do this before connecting any water valve lines at all. Tightly attach the faucet connection.

Installing Bathroom Vanity Plumbing (Floor)

In a typical scenario, the waterline usually emerges from the wall. But sometimes due to remodeling needs, you may need the process of plumbing the vanity through the floor. And that’s exactly what this segment is about.

Vanity water lines typically emerge from the wall. This is due, in part, to the locations of water lines inside walls. Wall locations are convenient because water lines can be tapped from both sides of the wall, meaning that vanity cabinets or toilets can then be placed back-to-back on opposite sides of wall in different rooms

Step 1: Vanity Installation

When the vanity cabinet comes without a bottom shelf that’s the right time to install water lines and vanity. A very unlikely scenario. With the typical one, you have a bottom shelf with a vanity. And so, you’ll need to drill it before installing water lines.

Use a 1-1/4-inch spade bit and driver or drill to simply make a hole through the bottom shelf. Take necessary measurements for making these holes. For each valve that is emerging from the floor, you need one hole.

Hold the vanity and put it over your made holes. Let the valves sit right through holes. Then normally continue the installation by using screws through the base. Start with top installation and end with faucets.

Step 2: Installing Bathroom Vanity Plumbing Through Floor

Your existing water lines in the floor or floor plumbing need to tap into the vanity and bathroom sink. For that, there should be a valve attached to the pipes. This basically caps the pipe and helps to turn off vanity whenever there’s a need.

The sink that is fixed on the vanity will have water lines from valves on the floor. You simply turn the water on with these installed valves to access.

Step 3: Water Supply Line

Locating the floor emerging water lines is not a tough thing to do. They need to raise at least 4 inches. Go more if possible. This is because the turn bottom shelf stays at least 3 inches above the floor. And so, a water valve penetrating from floor upwards and going through vanity’s bottom shelf is what the scene should be like.

You also want to decide on the hot and cold-water valves. Blue marking means cold water line. While the red one refers to the hot line. On both floor emerging valves, you should be able to locate threaded fittings.

Use thread seal tape and go for at least three wraps for all threads. There should be half-inch fitting on both lines’ end portion. You should find tiny bushing inside made of nylon here.

If not then get new bushings and insert them, screw one end to the floor valve and another end to the faucet end. Use your fingers to tighten them first and then go with a half-inch wrench to further tighten. And that should do.

Bathroom Vanity Frequently Asked Questions

Does a bathroom vanity need to be attached to the wall?

Most people love a wall hung vanity. They place their bathroom vanities against a wall because it is necessary to have plumbing to provide water to your sink and drainage for the used water, housing it against the wall allows for ease of installation.
Most people always love to have a vanity mirror above their sinks and a wall is a handy place to hang the mirror.

How do you fill the gap between a wall and vanity top?

If the gap is relatively narrow, such as half an inch thick or less, you can use a latex or silicone caulk to fill it. If the gap is wider, it’s best to include a backer rod. This is a thin foam-based tube that’ll help support the caulk so that it won’t form any holes.
If you have a larger gap or want to add more of a decorative touch to the space, you can also install trim over the gap. There are several different trims to choose from if you decide to use this option.

How much space should be between the side wall and vanity?

Many contractors and interior home designers will recommend a wall clearance of anywhere from 21-30 inches from the vanity. Often, a clearance of 21 inches is mandated by local building codes for safety reasons.

How do you hide plumbing under a floating vanity?

To hide plumbing under a floating vanity, you should install a cabinet, hide pipes with a storage bin, construct a small shelf, add a few potted plants to the decor, build a mini wall-cover, install a sink skirt or install pipe coverings.


And that’s basically all about how to install a bathroom vanity plumbing fixture. Both methods of the wall and floor connection work for different settings and your choice will depend on your bathroom scenario.

Make sure to get rid of all doors and drawers out before installation. Also pay extra attention when buying the new vanity, especially the measurements. Sometimes while removing the old vanity the clips do not come off.

And that’s when people try to break them off. You should be very careful if such a need shows up. Don’t end up breaking your sink.