So, have you disconnected power yet? Disconnected the battery, pulled fuses or thrown breakers to kill everything, and watched the tank?
Unless someones toying with you, or a hose is connected your not seeing, its impossible to get fresh water from salt water without a watermaker. Impossible.
Well, I can't see the hoses. If I went down into that bilge I'd never be able to get out -- folks would have to pass me food for the rest of my life --
BUT -- I figured it out.
Back in April, I had a significant fuel problem. A friend came over, climbed into the hold, nestled my fuel tank in his lap for at least five hours -- and cleaned the considerable amount of accumulated gunk out of it. He cut a hole in the top. I went to a local fabrication shop and had a cover and gasket (along with a spare) that would hold up to diesel fuel.
So my friend came back to put everything back together. He had had to disconnect several hoses to get the tank out.
He accidentally attached the scupper hose to the water tank, and the water tank fill hose to the scupper!
I finally figured this out. The dissolved kitty litter was the first clue. Then I pumped the tank out, after first marking the water line in the fine clay on the side.
The next day the EXACT same amount of water was in the tank. So I thought ... hmmm... the pumpout hose had gone into the cockpit and down the starboard scupper, since that's how she lists.
So I went to the store and got some red food dye. I saturated a folded piece of paper towel with it, put it over the scupper, and added water.
In the amount of time it took to do that, I went back down to the view port and found ... red water.
So my friend came back today, found the mistake, and re-connected the hoses properly.
I was honestly rather freaked out when I realized cockpit water was going into the water tank. Could have been very bad if we had had a storm like Sandy.
Thanks to all for your brain-storming. It really helped.