Photo of Wilden T4 - 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 40 GPM with 46 PSI and use 50 SCFM.   If the back pressure of the system were reduced, the flow would be increased.