Originally Posted by f1100turbo
Could not have been much of a tank and no vent to create enough pressure to bust.
I've dealt with the syphon issue as well. Added a 1" PVC Valve to the vent line. I close it when we travel and open once we reach our destination. Prior to adding the valve we lost 2/3 of the water in the tank on one trip. It was off-season so the water supply had been turned off at the campground. The road into the place was like a mine field, pot holes and just a bad road. The rocking back and forth allowed the water to run out the vent and it just sucked it down until the vacuum finally stopped.