I confused. Water should go from the well to the 1200 gallon cistern. There should be another pump in or by the cistern that pumps to the glass lined tank and then to the house. You should not be out of water if there is water in the cistern. Glass lined tanks don't usually go bad unless they have a hole in them. Water and pressure doesn't come from the pressure tank, it comes from the pump. More likely you have a pump problem.