an improved elastomeric pump for an infusion assembly . the pump includes a generally cylindrical mandrel body with first end , an opposed second end , a length , an outer diameter corresponding to a first radius , a central bore extending through the length , a first port extending from the outer diameter to the bore to provide a fluid passageway , a fill port and an exit port in fluid communication with the bore . the pump includes an inflatable elastomeric tube disposed concentrically about the mandrel , the tube being sealingly secured on the mandrel near the respective ends of the tube and having an original inner diameter that corresponds to a second radius so that it approximately matches the outer diameter of the mandrel , a length less than the length of the mandrel , a wall thickness such that : & lt ; t ≦.