Patent ID: 7351335

Claim:
A filter module comprising: a housing having an inlet for a liquid to be filtered and an outlet for filtered liquid; a first filter element accommodated in the housing, in the form of a tubular porous mass provided with a central through-opening, to which the inlet connects; and a second filter element accommodated in the housing comprising a number of lengths of tube-shaped filtering membranes formed as a winding into a tubular casing surrounding the first filter element and defining a cylinder shape having opposed extremities, a sealing material disposed at least at one extremity between the filtering membranes to terminate openings at the extremity between the filtering membranes, the outlet connected through the extremity; and wherein material is present between the windings of the tubular casing that can cause the formation of calcium crystals from the liquid to be filtered, and a part of the housing surrounding the tubular casing is provided with an inlet and an outlet for flush water.