Moving the pump intake line down to the drain port on the tank will only partially solve your problem as it's a virtual guarantee your tank is also sagging, a situation you can't see because of the enclosed underbelly. I suffered the same problem with my own Coachmen but fortunately it has an open underbelly so the problem was obvious ...
I solved the problem entirely by moving the pump intake to the drain port and adding a couple of steel braces to flatten out the underside of the tank when it's full. Now I can draw virtually
all the water out of the tank.
The fact your trailer underbelly is enclosed is irrelevant ... just cut it open, do the repair, then close it back up again.
FWIW, this isn't a
"design flaw" but rather a
"We can't be bothered doing any better and most customers won't notice anyway" attitude on the part of the manufacturer. :R
