My two cents
I was having all sorts of problems, i.e., bad odors, on my 1991 35.5H. I did the cloth test on the hoses--they did not seem to be in that bad of a shape--and nothing would seem to indicate that the tank is leaking. Granted, it is possible the hoses had something to do with the problems. However, following Peggy's advice and ideas from others, this is what I did: 1) I no longer use river or bay water to flush down waste. Instead, I keep a plastic cup in the head and fill it with fresh water from my tank to flush down waste. 2) At the end of the day, or at least two to three times a day if many are on board, I pour down a bit of CP (West Marine)to deodorize. 3) I religiously empty the holding tank every week and flush it with fresh water. 4) I use any of the two live bacteria ingredients to kill the bad odors.You will not believe the difference! I was already entertaining the idea of replacing the tank and hoses, but forget it. This year, it was as if I had placed a new tank; no odor whatsoever.