Some wells have water sources that are high in gases, carbonaceous or ther. The gases is coming from the source and collecting, or as also suggested, encouraged to separate by the anodes. There is only one theory – air is coming in and collecting; you need to catch it and eliminate it. It seems the lines are the highest spot for the air to collect, an air collector before the lines are in order. The old tanks without the bladder let the air collect there first.