The Duplex Pump Unit (FRS 660-11-DPU-UL) from RCI Technologies is the newest addition to that company’s line of diesel fuel purifiers and fuel recirculating systems (FRSs). Designed to automatically circulate and clean the fuel in customers’ fuel storage tanks on a preprogrammed schedule, the DPU features two fuel pumps, which operate alternately to circulate fuel through the system. Whereas RCI’s other FRS units utilize a single pump, the duplex pump offers backup in the event of a primary system failure. All FRS units employ filter-less technology. The control system is housed in a weatherproof, NEMA 4, key-lockable cabinet, and the system is equipped with alarms to alert the user in the event of pump failure, purifier high water level, system high pressure, or fuel catch basin leak. (