How to Install an Undermount Bathroom Sink
Replacing old bathroom sinks can give new life to your bathroom. Whether you're installing a new undermount sink, vessel sink, basin sink or a regular vanity sink, most of the steps will remain the same. If you're installing a pedestal bathroom sink, however, not all of these instructions will apply. All you need is a few tools, your new bathroom sink and a few detailed steps to replace that old sink and give your bathroom a whole new look.
Installing a Bathroom Sink:
1. Vanity installation: If you're installing a new vanity, make sure the countertop or vanity sink you use will fit to the top of the existing vanity. Once the vanity is installed, you'll be ready to install the new bathroom sink
2. Water shutoff: Turn off the water supply to the bathroom sink using the valves under the sink or the main water valve to the home. Undo the slip nut on the pea-trap (the U-shaped portion of the drainpipe). Have a bucket of water there to catch any water. Use the same bucket to catch water as you disconnect the flex-hoses from the water valves with an adjustable wrench.
3. Faucet installation: Every faucet and sink is different, so follow the manufacturer's instructions. Most bathroom sinks have three holes for a universal faucet. Faucets typically come with adapter plates to fit to nearly any sink. Be sure your bathroom sink and faucet are compatible. Apply plumber's putty to the adapter plate and attach it to the bathroom sink faucet holes according to the instructions. Then apply the deck plate over the adapter plate. Insert the faucet into the hole and attach the faucet from underneath with the metal washer and long nut.
4. Drain installation: The drain comes in four parts: the sink's threaded bowl-flange, the threaded flange-pipe, the drain tailpiece and the stopper assembly (which has several parts). Apply plumber's putty on the underside of the sink's threaded bowl-flange and push it down into the drain hole of the bathroom sink.
Screw the threaded flange-pipe from the bottom of the sink into the bowl-flange you just installed on top. Then screw the lock nut onto the other end of the flange.
Apply plumber's tape to the threads still exposed and screw the drain tailpiece onto the flange. There will be an opening for the pop-up lever on the tailpiece, which needs to face the back of the sink. Then install the stopper assembly according to the manufacturer's instructions
5. Sink to vanity attachment: Attachment may vary according to which type of sink you're installing, so follow the manufacturer's instructions for your bathroom sink. For a vanity sink
Apply a bead of caulk to the top of the vanity, where the bathroom sink will attach. Have an assistant help you lift the bathroom sink into place and press down firmly.
Re-attach the pea-trap and tighten the nut. Attach flex-hoses from the new bathroom sink fixture to the valves.
Wipe away excess caulk or plumber's putty with a wet sponge.
If the top of the bathroom sink touches the wall, apply a bead of caulk to seal the edge to the wall.