I'm trying to fix a slow leak which shows up in the area where the the hot water tank drain empties into. I know it's not the drain because I put a cup under the drain hose and it's dry. The water appears to be coming form the weep hole to the right of that drain, which is odd because that hole should be for water in that area to drain out and down to the bilge. The area where the water manifold and pump is located is dry., as are the adjacent bilge area.
Unfortunately in my experience the limber hole and hull liner system makes it really difficult to find the true source of water once it's under the liner. Best bet is just to look around every place you can check where water could be coming in before it gets to the liner. You could try putting paper towels at some of the limber holes to figure out which way the water is going.
I own a 2008 Beneteau 40 and had a freshwater leak. It turned out that the aft water tank was cracked somehow. I had done poor winterization or too much weight above it maybe. Who knows. The seal on the tank sensors can also be sensitive. Check under the floor boards in the aft cabin for this one. Just look anywhere there is a line. Since it is fresh water that is a clue. Pain in the ass project to find a leak.