A system (100) for delivering fluid to a wound therapy dressing (120) comprises a pump (130) comprising a vacuum port (138) and a positive pressure port (132), the vacuum port adapted to be in fluid communication with the wound therapy dressing； an expandable member (115) in fluid communication with the positive pressure port, wherein the expandable member is configured to exert a force on fluid within a fluid reservoir (110) to expel fluid from the fluid reservoir, the fluid reservoir adapted to be in fluid communication with the wound therapy dressing； and a valve (135) in fluid communication with the positive pressure port and the expandable member, wherein positive pressure from the positive pressure port is provided to the expandable member through the valve, and wherein the valve is configured to vent pressure to atmosphere.
