So I had a great idea! My overflow U-Tubes don't lose prime but they get air in the top which drastically lowers the flow through them. I hav a 4 head auto doser currently only using two heads. My DIY idea to keep the U-Tubes primed without having to suck the air out every two weeks or so - run a suction line into the U-Tubes and run 50-100 ml a couple of times a day from the tube to the outlet back into the tank.