A mechanical over-vacuum safety system and method of use for a vacuum pump system designed to extract milk from lactating mothers. The over-vacuum safety system includes at least one mechanical safety valve configured to reduce a vacuum in the pump system given an over-vacuum condition. The mechanical safety valve(s) may be automatically actuated in response to specific vacuum ranges, such as an over-vacuum conditions ranging between negative 350 mmHG to negative 300 mmHG. The mechanical safety valve may allow fluid flow by folding.
