If water is leaking under the sink, the basket strainer may not be tightly sealed. To test, close the stopper, fill the sink with water, and inspect from underneath with a flashlight and a dry rag.
If the strainer leaks try tightening the locknut using groove-joint pliers or a spud wrench (below). If that doesn't solve the problem, remove the strainer, following the steps on these pages. Either clean the drain hole and reinstall the strainer or install a new strainer.
A strainer made of thin metal or plastic may soon fail to seal water. A better-quality strainer costs more but will last longer. Installation is the same for all kinds of sinks: stainless steel, cast iron, or acrylic.
About 2 hours to remove a basket strainer and install a new one
Groove-joint pliers, spud wrench, hammer, plastic putty knife, screwdriver
Dismantling and reinstalling a trap
Make the worksite under the sink comfortable; position a bucket to catch water
New basket strainer, plumber's putty, replacement 1-1/2-inch rubber or plastic washers