A medical fluid line kit having: a length of tubing terminating at opposed first and second ends; and a valve mechanically retained on the tubing between the first and second ends, characterized in that the fluid line kit comprises: (a) a housing positioned between the first and second portion of the tubing, the housing provides an internal chamber fluidly communicating with a lumen of the tubing so that the internal chamber is positioned along a flow path between the first and second portions of the tubing; (b) a fluid blocking element positioned within the housing and resiliently biased to block fluid flow in a relaxed state and to permit fluid flow in a compressed state, the fluid blocking element is an elastomer element operating to prevent flow through the tubing in a relaxed state and to permit flow therethrough in a compressed state, and the elastomer element, in a relaxed state, fills at least a portion of the internal chamber to block fluid flow between the first and second portions of the tubing and which, in a compressed state, allows fluid flow between the first and second portions of the tubing; and (c) a plunger for compressing the elastomer element away from the flow path between first and second portions of the tubing in a compressed state so that fluid flow may pass around the plunger and the elastomer element is displaced away from the fluid flow. a length of tubing terminating at opposed first and second ends; and a valve mechanically retained on the tubing between the first and second ends, characterized in that the fluid line kit comprises: (a) a housing positioned between the first and second portion of the tubing, the housing provides an internal chamber fluidly communicating with a lumen of the tubing so that the internal chamber is positioned along a flow path between the first and second portions of the tubing; (b) a fluid blocking element positioned within the housing and resiliently biased to block fluid flow in a relaxed state and to permit fluid flow in a compressed state, the fluid blocking element is an elastomer element operating to prevent flow through the tubing in a relaxed state and to permit flow therethrough in a compressed state, and the elastomer element, in a relaxed state, fills at least a portion of the internal chamber to block fluid flow between the first and second portions of the tubing and which, in a compressed state, allows fluid flow between the first and second portions of the tubing; and (c) a plunger for compressing the elastomer element away from the flow path between first and second portions of the tubing in a compressed state so that fluid flow may pass around the plunger and the elastomer element is displaced away from the fluid flow. (a) a housing positioned between the first and second portion of the tubing, the housing provides an internal chamber fluidly communicating with a lumen of the tubing so that the internal chamber is positioned along a flow path between the first and second portions of the tubing; (b) a fluid blocking element positioned within the housing and resiliently biased to block fluid flow in a relaxed state and to permit fluid flow in a compressed state, the fluid blocking element is an elastomer element operating to prevent flow through the tubing in a relaxed state and to permit flow therethrough in a compressed state, and the elastomer element, in a relaxed state, fills at least a portion of the internal chamber to block fluid flow between the first and second portions of the tubing and which, in a compressed state, allows fluid flow between the first and second portions of the tubing; and (c) a plunger for compressing the elastomer element away from the flow path between first and second portions of the tubing in a compressed state so that fluid flow may pass around the plunger and the elastomer element is displaced away from the fluid flow.