Howdy Guys, thanks for the replies. I have two vent lines behind the road side duals, Chris at HL says they are tied into the other vent lines? I do not know if the fix they used to repair my tank is involved or something more complicated. I am working on getting it in to be fixed, I guess I am a little old fashioned, but I think it would be nice to fill the tank to full capacity and go camping without having to add valves, lose water or worry acout blowing out a tank by guessing every time I fill it. My literature, and partial motivation for my purchase,says it has a 75 gal tank, now I am told it is 63 gal with a 12 gal water heater? However timk in his detailed testing has a 73+- gal tank with the added valves etc.....I will get this sorted out a give a full report when completed.....UR