A bypass flow regulator for a vacuum waste system (VWS) is disclosed. The bypass flow regulator includes a valve assembly installable in an aircraft vent line leading outside the aircraft from an onboard VWS waste tank. The vent line directs an airstream pumped from the waste tank to an external outlet under suction (from which outlet the airstream is ejected from the aircraft). The valve assembly includes a group of valves (e.g., umbrella valves) set into the path of the airstream. The valves may collectively modulate the flow rate of the airstream by adjusting their effective flow area.