I tried a very simple "mod" this past week-end. On our 2000 Casita
Freedom Deluxe I removed the screen and it's retaining ring from the over-flow vent behind the water tank filler door. I slipped a length of vinyl tubing, which just fit the vent hole, about 3" down the vent. I left enough outside the vent hole so it just fit vertically inside the compartment. The door keeps the tube vertical when closed. The tank remained full after about an 80 mile drive. The only negative effect may be when draining the tank as the vent is restricted by the wall thickness of the tubing. By simply temporarily removing the tubing when draining, that problem will be corrected.
I wonder if the small size of the vent is what is causing the slow draining? I'll try to remember to try blowing in the end of the vent tube when it's draining next time. That might indicate if a larger size vent would help.
It's an interesting problem, the top of the tank and it's filler/vent are limited by the bed on our TT. If the whole filler assembly were moved behind the stove/sink cabinet, installed as high as possible behind the drawer, the current problems might no longer exist. Of course one would then have to use a longer hose to reach the new filler location.
What other solutions have any of you come up with?
& Ann K.