A vacuum controlled liquid delivery system, including a primary chamber; a manifold assembly affixed to the primary chamber, the manifold assembly comprising a feed line and an external pressure line; and a cap configured to reversibly engage the manifold assembly at one end and reversibly cap a syringe at another end, the cap comprising a septum and a porous plug, wherein when the cap is attached to the manifold assembly the feed line passes through the septum, and further wherein the porous plug seals upon contact with a liquid.