Eldex pumps are designed to maintain precise flow against significant back pressure. Back pressure is critical for the performance of Eldex Optos pumps, which achieve precise metering through a positive displacement, reciprocating piston driven by a stepper motor. The pump relies on ball and seat check valves to control fluid flow, requiring a minimum outlet pressure of 25 psi higher than the inlet pressure to ensure proper valve seating. This pressure differential allows the inlet ball to open during the piston’s suction phase, filling the chamber, while the outlet ball seals to prevent backflow. During the delivery phase, the outlet ball opens to release fluid, while the inlet ball seals. Insufficient back pressure can disrupt this process, causing fluid to flow through the pump without accurate metering, leading to inconsistent flow rates.