I had an issue with them flooding when I started using them as well. I never really figured out a fool-proof solution, but I did notice that when I was out-and-about or stressed somehow, I would draw harder on it. So I learned to regulate my drags so that I wasn't pulling the liquid straight through.
Sometimes I could blow the excess liquid out through the bottom, but only if the
tank hole was plugged by pushing the carto down a bit, or emptying it.