A pump system for the subcutaneous delivery of a liquid medicament, having apump module (10) comprising a stator housing (28) with a chamber (30), a rotor(32) rotatably and axially slidably received in the chamber and comprising afirst axial extension (46) with a liquid supply channel (50) and a secondaxial extension with a liquid supply channel (52), the first and second axialextensions having different diameters, and first and second sealing rings (54,56), mounted around the first and second axial extensions.
