Ours is a 1992 Monaco , the bus has been inside all winter,I just got it in the fall and looking everything over . I air tested the water system before putting any water and found it had not been winterized ! Or not done right if it was ? Since the plywood under the rubber is wet I am think I’ll remove the gray water bank next and see what I find? Fresh water tank is ok. I put treatment in the solid tank and I am not getting any smell good or bad so I hope it’s not that one!