Step 8 · Test for Leaks and Apply Caulk
With all connections made, it's time to test for leaks. Place dry paper towels under all connections (supply lines and drain trap). Slowly turn on the shut-off valves, one at a time, and let the water run. Use a flashlight to carefully inspect every connection point for any sign of dripping. Check the connections at the shut-off valves, at the faucet tailpieces, and all joints of the P-trap. Fill the sink basin completely, then release the pop-up drain to let the water rush out. This pressure-tests the drain connections. If any leaks are found, turn off the water and gently tighten the leaking connection a little more. Once you've confirmed there are no leaks, apply a bead of silicone caulk along the back edge of the sink where it meets the wall and around the base of the pedestal where it meets the floor. This seals gaps and adds stability. Smooth the bead with a wet finger or caulk tool.