A port assembly includes a housing with an opening and a bore therethrough, a slit septum disposed in the opening to control access through the opening, a base joined to the housing and having a membrane attached thereto, a perforator having a first end abutting the slit septum and a second end aligned with the membrane, and a resilient member disposed between the perforator and the base. The perforator has first and second lumens, the first lumen extending between the first and second ends of the perforator and the second lumen extending between a point between the first and second ends and the second end. The perforator also has a seal disposed about the first lumen at the first end of the perforator, and a valve associated with the second lumen to limit flow of fluid through the second lumen in the direction of the second end.