mbinkley - seriously do you have any nugget of a clue what your talking about?? The only way you would not need a vent line on a gas engine or a pressure line on a nitro would be if you were using a balloon to hold the fuel. When you take fuel out of a semi rigid structure such as a fuel tank it has to be replaced with something like say AIR from the atmosphere or exhaust gas on a nitro motor.

I personally use two and three line systems, just depends on the plane. I use three lines on all my gas engines because I use the Walbro felt clunk rather than adding a filter in line introducing 2 more points of possible air leaks. As for tying the clunks together, never have and have never had them get tangled. As for two lines, I have a couple of trainers where the line attaching to the carb is real handy so no need for a T, just pop the line of the carb and refuel through it. On others I use a T with a set of forceps to pinch the line on the carb side of the T (I place 1 or 2 layers of shink tubing over the line where I pinch it to prevent the forceps from damaging the line) and a short piece of line to a good quality fuel dot. I have tried a couple types of easy-fueler devices and had inflight failures on both causing dead stick landings. However with that being said there are many members of my club that have been using various forms of them for many years and never had a hiccup.

So like someone said earlier, 2 lines, 2 lines with a T, 3 lines, easy fueler valve - all a matter of opinion. Spend a few extra minutes setting your system up, use the right type and size of tubing, make sure that all the joints are done properly, check the system for leaks (and if your using one of the big-name tanks like Dubro or Sullivan or most of the supplied ARF varieties check and triple check where the stopper goes into the tank to make sure its sealed and that the tank hasn't split on the molding seam), check everything again and go fly.