My husband is a Concrete Pumper. He uses scuba tanks to blow a nerf football through his hoses to clean them out. We are having to fill 14 large tanks about twice a month. We have figured out that it's costing us $1600 or so a year in air costs alone. We have decided to purchase our own compressor to fill them. Since we won't be worried about air contamination (No one will be breathing the air in the tanks), is there any cheaper options out there for us? Any way to modify a cheaper compressor? If we go with a new Scuba compressor, which one would you recommend? Any good place to find a used one besides E-Bay? Thanks in advance.