rated current of 2 0 amps and a stall current of 6 0 amps the housing 30 pump chamber cover 40 connector rods 58 and 59 face cam 44 and head plates 72 75 are anodized aluminum providing for the low weight of the pump 12 the diaphragms 76 and 77 are preferably a fluorosilicone coated fabric material having a minimum shelf life in excess of ten years the rollers 52 and 53 are a thin dense chrome and the roller bearings 48 are standard steel bearings and the springs 56 and 57 are suitable compression springs the inlet check valves 20 and 21 are a deflecting reed type valve for low inertia and pressure drop across the inlet ports 86 and 87 preferably less then 1 0 psid at 400 pph the outlet check valves 22 and 23 are preferably spring loaded flat poppet type valves the poppet springs 96 and 97 bias the respective outlet check valves 22 and 23 to close the outlet ports 88 and 89 in the event of positive tank pressure the inlet screens 90 and 91 preferably filter particles larger than 100 microns this construction provides a pump 12 that is rated at 300 pph with a maximum of 400 pph and a controllable flow range of 20 400 pph correlating to a 20 1 turndown ratio the pump has a rated pressure rise of 30 psid and the speed ranges from 0 to 4 200 rpm the pressure at motor stall is 190 psid minimum at u2212 40 degrees f referring now to fig5 and 6 operation.