Refill rate refers to the speed of the piston retraction during the pump refill stroke. Full Out refers to a maximum speed refill designed to minimize pulsation. With DI water in particular, this rapid refill can pull gas out of the fluid, leading to bubbles in the plumbing and pump cavitation. Adjusting the refill rate, which refers to a % of the time in pumping stroke/refill stroke, the rapid refill can be slowed down – hopefully preventing this degassing. i.e., 50/50 refers to balanced pump cycle times – 50% pump stroke, 50% refill.
