Model 125 and 125-27, designed primarily for booster pumps, are installed inline, on the discharge of the pump. They are normally closed with the pump off, open slowly after the pump starts, and close slowly prior to pump shutdown. In this way, flow is slowly and smoothly transitioned to and from the system. These valves also include a check feature that will close the valve in the event of a power failure while the pump is running. Thus, they eliminate any need for a separate pump check valve.

Model 126, designed for deep well pumps, is installed on a bypass line between the pump discharge and the pump check valve, and discharges either to waste or back into the well itself. It is normally open with the pump off, closes slowly after the pump starts, and opens slowly prior to pump shutdown. In this way, flow is slowly and smoothly transferred from the bypass to the system, and vice-versa.