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 (R mandrel ), 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 (r) so that it approximately matches the outer diameter of the mandrel (R mandrel ), a length (L) less than the length of the mandrel, a wall thickness (t) such that: (0.4225 x r) < t< (0.660 x r).
