On a chilled water system I have installed a pump which is designed to 65 ft head @ 137 GPM on the pump manufacturers curve. I am getting 46 Ft head 91 GPM and a pressure differential of 20 psi (34 In 54 Out) from the pump. It's a Taco 3009 KV series pump @ 1760 RPM and the inlet outlet piping sizes are as specified at 3". Does anybody know any possible problems that may be causing this?