Hi Ms Hall - Read your latest book ( a Christmas present )- loved it - makes so much sense! In order to add a second vent line to the holding tank ( 1985 Catalina 27 - V Berth located tank ) , can an inspection port be added, to access the new thru bolted nylon vent fitting, ( and also to aid in cleaning the tank ), without causing tank failure during pump-out function ? Or can the new vent line be self-tapped into the tank at center line as you described ? I've located / eliminated most odors, getting to the end now. Thank you very much, Jeff ( on L. I. , N.Y. )