2006 Okanagan 116ULT access panels to basement

I own a 2006 Okanagan 116ULT truck camper. Love it by the way. We have sprung a leak in the basement of the camper. We can see the cascade of water coming in from the fresh water tank area, which way in the front of the camper. Is there an access panel hidden somewhere to get in there? There is no possible way even a toddler could get in there so there has to be a panel somewhere. We had a leak from the same area a year or so ago and took it to the dealer and they fixed it for a big price. It is possible that this is the same fitting leaking again. At that time I should have pressed the dealership harder to find out where the access was but what he did say was that it was under the bathroom sink area sort of. I should have had them show me, but they weren't too interested in providing that information. Any clues? Is there any help out there? Thanks