Are the fresh, grey & black water tanks on an RV securely fastened all around (including top) or only supported bottom & sides?
Reason for question: Wondering if 'loose' freshwater tank punctured/worn thru, if it could bounce around that much. If tanks not secured on top too maybe they can bounce up far enough to have been damaged?
Last camping trip DW followed with the boat, said she saw water coming out from underneath rear of 5er. Brought it to dealer, they couldn't find anything but admitted they didn't take off the bottom 'insulation' to check - they only couldn't find any water coming out when they filled the tanks. When camping/parked there's no evidence of leaking; only see it when moving, and from DW's description it's not a whole lot but still very noticeable.
Fuzion toyhauler, self-installed wheel chock in garage directly over one of the freshwater tanks with lag screws that protrude ~1/2" below floor. There's 3-4" space between bottom of floor and top of tank.
We always depart the house with full freshwater tanks.
It might not be as bad as you think. Many FW tanks have an overflow tube that can spill water when the trailer is moving down the road and water is sloshing around. There are threads on this forum where people report losing nearly 1/2 of their tank capacity by the time they get to their campground. So that is the first avenue to investigate. Note: there are also several fixes for this problem given on the forum.
Or it could be that you do have a leak. It could be an actual hole or crack in your tank, but more likely a loose fitting or hose. I had this same problem. It is difficult to identify if you have a full underframe cover, which I had. I pulled to the shoulder of the road, the TT was at a steep angle and water poured out between the frame and the underbelly cover. I had to pull the cover and found a hose that ran between my two water tanks was loose and leaking water.
Best thing to do is fill it full at home and let it sit for a day, then crawl under and take a look. This may involve pulling at least one side of the underbelly cover so you can get a good look in there.
If it just loses water while on the road, I would suspect it is your overflow tubes, and not an actual tank leak.
