I have just set up co2 bottle after 2 years of using a Carbo plus which was rubbish. I have a Denerrle crystal co2 bubble counter. When I set it up I half filled it with water but when I looked this morning it was completely full of water. It seems to work ok but i was wondering whether it should be half full or completely full. I have the Dernelle crystal non return valve placed under bubble counter and then a non return value near the co2 cylinder so no probs with set up. Any views. Thanks