I am cleaning up the sanitation system on my Ericson 32 after years of neglect by previous owners. First check the holding tank vent ( somewhere topsides). These small vents are often clogged with old spider nests and such. Then make sure none of the connections to the tank leak. Older systems had (disgusting) recirculating lines back to the head instead of using a raw water intake for flush water. And old hoses will allow odors through even if they don't leak. If the hose from the head or to the cleanout have never been replaced, then you gotta think about biting the bullet and doing so. Unfortunately, good sanitation hose ain't cheap.
