Finding a Leak
Before you can stop a leak, you have to find its source. That can be tricky. Water that escapes your pipes can travel a long way before it drops onto your cabinet's floor.
Here's how a drip detective tracks the source of a leak: Fill both bowls of the sink with lukewarm water, not cold. (Cold water can cause beads of condensation to form on the pipes, making it impossible to find the leak.) Then get under the sink with a trouble light. Dry off all the pipes and examine the seals around the basket strainers. If you don't see any droplets forming, remove both sink stoppers and watch for telltale dribbles.
Joints are the most likely source of leaks, but old metal pipes can develop pinhole leaks anywhere, especially in the trap. If you can’t find any leaks in the drain system, check the water supply lines that serve the faucet. Finally, check for “splash leaks,” spots where water seeps under the sink rim or faucet base. To find these leaks, use a rag to dribble water around the faucet and sink rim, then get underneath and look for drips.