Use a turkey blaster or a syringe on the end. Anything that can pull a slight vacuum on the end should start the flow of water. Make sure that there is a tight air seal around the end or you will not be able to pull a vacuum.
In a bladder-tank, you can only "read" the pressure TANK residual with the water off and the tank empty of water, leaving only the air-pressure in the top portion. If...
Using a mylar (foil) balloon is actually safer for two reasons. First, it is easier to control how much helium you get. Second, there is no talcum powder inside the...