Vessel sinks, popular additions to home bathrooms, are mounted on top or just below the bathroom counter. The impression they give is a simple bowl, or vessel, set in place ready to catch the water from the faucet. Below the surface, these type of sinks are just like any other bathroom sink, requiring a drain connection to dispose of water running through the sink. One of the best ways to fix a vessel sink drain leak is to disassemble the drain and check the components.
Clear out the space beneath the vessel sink to give yourself enough room to work. Remove any towels or other supplies that may be stored beneath. Open up cabinet doors, if present.
Place a bucket underneath the curved pipe (P-trap) in the bottom of the drain. Use a wrench or pair of pliers to loosen the couplings at either end of the P-trap and pull the trap out of the adjacent pipes. Empty the water inside into the bucket.
Unscrew the retaining nut on the underside of the sink, using the pliers. Pull this off the drain pipe.
Place a block of wood against the bottom of the drain pipe and gently tap it with the hammer. The goal is to knock the drain loose from the vessel sink above without damaging the pipe. You can also try using a rubber mallet.
Clean out the drain opening in the vessel sink. Use a sharp knife to cut away any silicone caulk clinging to the drain opening. Clean up any mold or mildew with a bathroom cleaner and rag or old towel. Dry the drain opening thoroughly.
Insert the caulk into the caulking gun. Cut off the end of the caulk tube at a 45-degree angle. Squeeze the trigger on the caulking gun gently and apply a bead of caulk around the perimeter of the drain opening. (You may need to poke a 16-penny nail down through the tip of the tube to start the caulk flowing.)
Check the rubber washers on the vessel sink drain. If any washers are worn, replace them.
Insert the drain into the opening in the vessel sink. Turn the drain slightly as it contacts the sink surface to help distribute the caulk.
Move so that you are underneath the vessel sink and can see the drain protruding through the bottom. Slip the retaining nut over the end of the drain. Hold the drain steady with one hand while you tighten the retaining nut first by hand, then with the wrench.
Apply pipe thread compound to the threads on the bottom of the vessel sink drain and the sewer inlet. Slip the P-trap back into place between the pipes. Tighten the couplings by turning clockwise with the pliers.
Run water in the vessel sink. Check the pipes and the drain as the water runs to ensure there are no leaks.