Out of fresh water at a half tank

[Plowtoy]

Took out our 1997 314BHS for its first weekend since we have owned it. We rarely camp at parks with full hook ups, so almost always fill the fresh water tank. I sanitized the water system since the water smelled while I was getting the camper cleaned out. I filled the tank to capacity Wednesday afternoon with the bleach/water solution, ran it through all the faucets until I could smell it, and Thursday we drove from our place to my folks place 10 miles away. Once we got there, I pulled the fresh water drain valve and watched the water start to drain. Figuring we had a 2 hour drive to our campsites, I thought I would get most of the solution out and fill and rinse the tank at the park. Got to the park, closed the valve and noticed that the tank still had about 2-3 inches of water in the bottom. I filled it and told my wife that we shouldn't drink the water over the weekend, just use it for washing our hands and dishes. So Saturday morning comes and the pump is running dry, so I again check the level and find there is still 2-3 inches of water and the indicator still shows half a tank remaining. I opened the winterizing valve and blew through the hose and was able to hear bubbles in the tank, but couldn't really suck any water through. I refilled the tank and it worked perfect again.
The outlet (that goes to the pump/drain) from the tank is on the bottom side (underneath), do you think for some strange reason, on the inside of the tank, there is a hose sticking up to not allow it to drain completely. At this point, I don't know how you would ever drain the tank enough to prevent it from freezing in the winter??? It feels like maybe the nipple can be unscrewed from the bottom of the tank, but being plastic, I haven't tried. Any ideas??? Sorry for the long post! Dave

[Plowtoy]

Just an Update!
I pulled the fresh water tank last week. I found inside the tank where the outlet screws in, there is a "filter screen" about the diameter of a dime and about 4 inches tall. I was able to remove it (by damaging it) and found that over the years of use with well water, alge had formed and plugged it mostly off, causing it to suck air once it got to the point of not being submerged. I did not reinstall it, and figure I will take my chances with out it. We dont normally drink the water from the tank anyway. Hope this helps someone, someday! Dave

[Heady]

Thanks for updating us on your fix Dave. Hopefully this will help others experiencing this same issue.