What size is your tank? Last year, when I had my tank refurbished, it took me only 2 gallons to get me started and to the nearest gas station. There is a 'flower pot' (as named by Dr. Benz) in the middle of the gas tank [search for 'fuel tank tour' by Joe Alexander and all will be clear]. This is where the feed line exits to the fuel pump. If the little feed hole at the base of the flower pot (to let gas into the flower pot from the rest of the tank) is not fully clear of debris, then it might take a while for gas to seep through to the flower pot. This might have looked as if it required more gallons of fuel, when it was just more time that was needed in order to allow enough fuel to seep into the flower pot. This is just a guess.
I generally use a good set of hose pinchers to avoid having to mess with the fuel tank when working on the fuel pump. Last year I swapped out three different fuel pumps while debugging a fuel issue, all without draining the fuel tank.
My favourite kind of hose pinchers are these:
http://www.autohausaz.com/search/product.aspx?sid=wdbl5i551b2bub55d3mb52vw&partnumber=22850LISLE