Remove shower unit for repairs
The shower can be disassembled. There is an exploded diagram available from one of the Winnebago websites. It sounds like a hose or cracked hose fitting somewhere. I found a small hole punched into the line that comes from the shower "power" drain to the pump. The factory had cut a square corner in the luan panel under the forced air furnace (where the hose passes through). With time and vibration it made a hole but this would only leak when the power drain was on. In your case it could be fittings at the faucet above the toilet. Do you use it? Then there is the drain stopper hidden in the trough behind the sink to the right of the trough. Mine was closed at first which caused the trough to flow down the wall behind the toilet. Then, of course, the toilet fittings. The toilet could have a small crack that is not visible. (Replace toilet?). Doesn't sound like the holding tank is cracked unless it was much too full when you noticed leaks? As a habit, when I turn off my water pump, I always push the small toilet pedal (water filler pedal) for a second or two. This relieves pressure in the system when I leave the Rialta alone for a few days. If one doesn't do that and temps go up it only puts the lines under more stress. The toilet has quite a few seals and working parts including many O-rings. I'll be curious to find out what you finally come up with but yes, there is a large access panel behind the toilet. One other question: Does this happen when hooked up to a water hose, or when the water pump only is being used? Best of luck and hope this helps somehow!