We purchased a Catalina 400 from the states, and the holding tank for the main head had been removed and a salt water discharge system had been installed which although approved by the US Coast Guard it is not permitted in the Great Lakes. We are currently using the forward head which does have an 18 gallon holding tank, but have been unable to locate a tank for the main head. We would appreciate if anyone has a suggestion as to where we might obtain an holding tank for this boat.