Allentown's air powered GBP-500 Water Booster Pump delivers a maximum of up to 10.6gpm (40 lpm), while the GBP-300 delivers a maximum of up to 20gpm (76 lpm). For both models the minimum air pressure required is 20 psi (1 bar) and the maximum air consumption is 80 CFM. The water pressure can be varied from 0-500 psi (0-34.5 bar) depending on the air pressure regulator setting. The pump works on a reciprocating differential area piston principle.