We've had a persistent problem that 2 plumbers have tried to fix, unsuccessfully. The 2 plumbers tightened areas under the sink near the hot/cold water valves.

In the downstairs bathroom, there is a fresh water stain on the wood on
The bottom and side boards directly under the sink which I can see when I open the cabinet doors. The wet stain stretches horizontally all the way across from left to right and up the sides on the left and right under the sink. I've been told by one plumber to use silicone to seal between the actual faucet and sink, and around the hot/water knobs at the top of the sink, which I did, but the leak is still occurring. The area dried out a little after the plumber came last week, but is wet again today. What else should be checked?

Thanks in advance for any advice!

I don't care if the plumber's only been in the trade for two weeks, you take toilet paper and start at the top and wipe around until you see moisture show up. This is basic 101 plumbing. Now if they can't locate the leak the first thing to do in to shut the water off and let everything dry off. Then turn the water back on without running anything. If you see moisture track it back. Did the plumbers pull the faucet and inspect the brass valve body for leaks? If there were a crack in the brass valve body this leak would be hidden. The plumber that told you to use silicon jell to seal around the stems and cover plate wasn't attempting to repair the leak he was hoping to get lucky and contain it. Go back to square one and start from scratch. Remove the chrome cover plate on the faucet and expose the innards of the faucet and see if the leak doesn't come from there. What bay area are you from? I live in the Tamps Bay Area. Good luck, Tom

From the pictures attached to my original posting, does the water stain pattern look like something common with a faucet leaking? Is it possible there is something else leaking, like a pipe next to the wall?

One of the plumbers just splashed water onto the top of the sink to diagnose the problem. Since our home warranty didn't cover faucets, he "couldn't" check the faucet to see if the faucet was the source of the leak. He suggested the sealing with the silicone gel, but I wasn't told that the faucet could have been
A source of the problem. As you suggested, I will dry out the area and look at the brass valve body.

Thanks so much from the SF Bay Area! Have a great weekend!