In my forward cabin under bed space, I am getting a very small amount of fresh water, not enough to think that the water tank is leaking - but enough to be annoying.
I am wondering if the under bed space (given its a cold area with direct exposure to a cold water tank and the hull) suffers from condensation? Having just fitted a complete heating solution the boat is now a lot warmer and quite possibly causing an increased issue in this space.
I'm also trying to work out where a leak is coming from that places a tiny amount in the central bilge (but nowhere else) again fresh water - is there a check list of go-to leaky areas? (I've checked forward water tank pump and replaced).
Your recently fitted “complete heating solution” may well be the problem, or it might be a bit of a red herring depending on exactly how it has been fitted. Do you have any heating pipes passing through the under bed space? If yes, then condensation might be the problem. If you have no heating pipes going through that area then it’s most likely to be fresh water leakage from,
1. A leaking rail stanchion base,
2. A leak from the forward cold water storage tank,
2a. A leak from the cold water pipe connection to the tank,
2b. A leak from the tank lid seal perhaps not sealing, lid not shut tight,
3. A leak in way of one of the deck fittings, though that should also make the bunk cushions wet as well.
You don’t say which boat you have or the year in which it is built, or how your recently fitted heating system relates to the area where you have found fresh water, so it’s difficult to be specific about the most likely cause.