The answer to whether you need to drain pump supply lines depends on where you live. If you live in an area that does not typically have frozen ground, the use of a check valve is common. A check valve is included in the discharge assembly to prevent drainback through the pump after a dosing event. Drainback through the pump may cause bearings to wear out more quickly, shortening pump life. This would typically be an issue if the pump was turning on while drainback is occurring (which is not common). In this case, a vent hole (air release) must
