Ouput weight for ballast tanks

I am looking for weights of outputs rather than flow rates eg, when i fill a gas bottle the weight increases because it is pressurized, so we have weight, I want to make pneumatic ballast tanks to hold 1.2 tons of weight from compressed air. I need to be able to do this in about a minute. so I read your charts and they make no sense unless you have forgotten to write compressed air per hour, because 52cfm is jack shit, a 20 dollar water pump can move 6000 litres or 6 ton per hour, i find it hard to believe the large $10,000 compressors cant beat a $25 water pump in fluid dynamics, what am i missing here? and what machines an fill ballast bottles or air bottles at 1,200 litres compressed weight or 1.2 ton, need kilowatts not horsepower