Originally Posted by sailingdog
You really don't want to have the fuel vent line on a switch...better to leave both tanks properly vented...
CD's just making sure we are awake.
If you fill your tank from a marina with a (cold) underground fuel tank on a hot day, the fuel will expand soon after. And with a full tank, there will be relatively little air above the fuel to absorb that fuel expansion (via an increase in air pressure). So the pressure in the tank will get pretty high until BANG you burst your very full fuel tank.
(BANG added for emphasis and color. Haven't really ever burst one of those, they may go BURP or CLANG for all I know.)