How to Repair Leaky Sink Base Plates

Remove all of the items from under the sink so you can have room to move. Tighten the mounting nuts. Use a pair of slip-joint pliers or a basin wrench. Don't overtighten the nuts. Turn the water on and see if there's still a leak from beneath the base plate.

Loosen the mounting nuts enough to raise the base plate about ½ inch above the sink, if the water is still leaking. Clean any gunk around the base plate. Stuff plumber's putty under the base plate and re-tighten the mounting nuts.

Check for leaks. If there's still a problem, you must remove the faucet. Turn off the water and drain the water lines.

Unscrew the mounting nuts again. This time disconnect the water lines. Take the faucet off the sink. Remove all the putty. Make sure you don't scratch the sink.

Buy or make a new rubber gasket for underneath the base plate. If you have to make one, find a piece of rubber that is the same thickness as the old gasket. Use the old gasket as a pattern.

Re-apply the putty. Put the faucet back on the sink and reconnect the water lines. Turn on the water supply again.