Installing a New Bathroom Vanity


In this video, Do It Best Hardware goes over the steps necessary to install a bathroom vanity.  They give a lot of tidbits, for instance not to start this project late in the day in case you need to make a run to the hardware store.  This gives you the heads up to expect issues so you are not surprised.  The video also goes over the current plumbing that is a strange arrangement and tells you to accommodate with what you have or start over.  Another key thing here is a 12” flexible supply line giving you the extra flexibility to fit in a tight area. The video definitely makes it look easy enough for anyone to do.  I would recommend having phone numbers on hand in case you need assistance.  Last key point is to continue checking the plumbing to make sure there are no slow leaks.


To do this project you need some basic tools and supplies, as well as a new vanity and faucet. The tools you will find helpful are an electric drill or cordless screwdriver, a utility knife, an adjustable wrench, plumber’s putter, silicone sealant, a caulking gun, a new sink trap, a trap adapter that will connect from your tubular plastic trap to whatever type of drainpipe comes out of the wall, flexible supply lines and possibly new quarter turn chrome shutoff valves.  It’s also a good idea to have a bucket or pail handy to catch any remaining water that might drip out of the traps or valves.

You will probably need a light source to illuminate under the sink as well.  In some cases, a pillow under your back, while you’re lying on your back looking under a sink is not a bad idea either.  Since you never know what you’ll encounter when you tackle existing plumbing, I recommend not starting this project too late in the day.  Most plumbing projects take far longer than people anticipate. The first step in the project is to shut off the water supply to the old vanity. Then you disconnect the supply lines from the existing valves and detach the old drain trap from the drain pipe coming out of the wall, or through the floor.

Once this is done, remove the sink from the vanity top, then remove any screws holding the vanity top to the cabinet, and then the cabinet to the wall.  Next, use the utility knife to separate the cabinet top from the wall.  You will often find that there is a bead of caulking or sealant along the top edge of the vanity backsplash, where it meets the wall, and along the floor, where the base cabinet sits.  Even if there isn’t any sealant, there can be paint that will stick the top against the wall, and failure to break this bead can lead to damage to wall surface while removing the vanity.

Once this is done, remove the vanity top off the base cabinet, then remove the cabinet.  As you can see in this project, there’s a rather strange arrangement for the existing supply valves that feed the faucet. It would have been better if they  had attached the angle stops to the copper pipes right after they came out of the wall. But when you encounter odd situations like this, you have to make a choice, either work with what you have, or replace everything and start over. Most people will try to work with what is there, and that is how this project will proceed.

After that’s done, clean up the floor where the new vanity cabinet will sit. You will have to connect the new trap assembly to the existing drain coming from the wall. A P-trap  is composed of two parts, the J bend which is the curved part of the trap and the wall tube, which connects to the drain pipe coming out of the wall. To connect the wall tube, slip the threaded nut and the beveled gasket on to it. In this house the drain was an old galvanized pipe. Since trap adapter nuts are standard pipe thread, you can simply connect the trap directly to the drain pipe with a nut and slip joint washer.

Another option would be to buy a threaded trap adapter and screw it on to the pipe, then connect the tubular plastic pipe to that. After the wall tube is connected to the drain pipe in the wall, you can put the new base cabinet in place. You mount the faucet to the sink, before mounting the sink in the base cabinet, it’s much easier to fasten everything you can to the sink before dropping it into the vanity top, since you have little room to work under the sink once it’s mounted.

While the sink is out of the cabinet, it’s easier to connect the supply lines to the faucet, once you drop the sink on to the vanity top, you can connect the supply lines to the shut offs. Since the shut off valves are functioning well, we will connect the new supply lines from the faucet to the angle stops. Be very careful not to over tighten the nuts onto the faucet or to the shut off valves. Using an adjustable wrench, tighten until the supply line appears firmly connected. This would be a good time to put a pail under the drain and run the water to see if there are any  leaks. If it leaks slightly you can always tighten it another one quarter turn until it stops dripping.

When you set the sink on to the base, I find it’s a good idea to put a bead of caulking sealant between the sink backsplash and the wall to keep moisture from dripping down behind the cabinet and causing mold.  This would be a good time to paint the bathroom walls if painting is part of your remodeling plans.  In this project they selected twelve inch supply lines instead of nine inch so they would have the needed flexibility to make a loop, so it would fit in a very tight area. Although a shorter supply would seem the right choice, you’ll not be able to bend it enough in this limited space.

To mount the pop-up drain assembly, unscrew the top piece from the assembly and put a bead of plumbers putty under the piece that goes inside the sink.  Press it firmly into the sink drain hole then connect the rest of the assembly by screwing it onto the top piece from under the sink. You can do this after you put the sink into the base cabinet, but I find it easier to do it before you mount the sink into the base. To connect the rest of the pop-up assembly, you drop the pop-up lift rod through the hole in the faucet and connect it to the pop-up assembly rod under the sink. The lift rod slides through a  piece that will slip over the pop-up assembly rod and fasten to it, so when you pull the lift rod up it will close the drain plug, and when you push down all the way, it will lift the plug and let the water out.

Test it to make sure it moves the drain plug inside the sink up and down freely. It will take some minor adjustments until you get it just right. Now you can finish connecting the J bend on the trap to both the trap arm and the pop-up assembly pipe.  Once you complete this step, reach under the sink and turn the shut off valves back on to check for leaks. If there are no leaks, check again in a few hours and again the next day, to be sure no slow leak appears that could cause mold to form  under your sink. Now stand back and admire  your handy work. In a very short time, you have greatly improved the look of a bathroom at a very reasonable cost. Hiring a professional plumber is a wise idea in some cases, but this is a project that most do-it-yourselfers can tackle themselves saving a lot of money.

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