Photo of Wilden T2R - polypropylene - with brass air valve

Performance is a balance of the incoming air supply pressure and quantity (SCFM) verses the piping system resistance. 

As example -- with Teflon diaphragms 80 PSI air supply - would pump 20 GPM with 50 PSI and use 30 SCFM.   If the back pressure of the system were reduced, the flow would be increased.

The use of a solenoid controller can provide for a fixed flow rate.