The invention relates to a method for producing a membrane reservoir with a metal case. The inventive method comprises the following steps; a) rotating a tubular piece around its longitudinal axis, b) preheating one end of the tubular piece for deformation through heat retraction by strain-hardening, c) strain-hardening the end of the tubular piece by applying at least one pressure tool, selectively heating the target area of said pressure tool to deformation temperature in order to form a floor at the end of the tubular piece with an opening at a collar, said collar being turned outwards, d) forming an inner circular groove in the central area of the tubular piece, e) introducing a membrane system, said membrane system being sustained in the circular groove by a corresponding clamping ring, and f) forming a second floor at the second end of the tubular piece according to steps b) and c).