Method for operating a water softening system having two calibration characteristics and associated water softening system

A method for operating a water softening system (1) having an ion exchange device (6), comprising:

• an ion exchange resin (5), a supply vessel (8) for supplying a regenerating solution (7) for regenerating the ion exchange resin (5), an admixing device, and at least one flow meter (13, 14, 17),
• wherein an influent volume flow V(t)raw of raw water towards the water softening system (1) is divided into a first partial volume flow and a second partial volume flow upstream of or within the water softening system (1), with the first partial volume flow being guided through the ion exchange resin (5) and that softened partial volume flow V(t)partial1soft being admixed to the second, raw water-bearing partial volume flow V(t)partial2raw, whereby in or downstream of the water softening system (1) an effluent volume flow V(t)admixed of admixed water is formed,
• wherein the ratio between the first and second partial volume flow in the effluent volume flow V(t)admixed of the admixed water may be adjusted via the admixing device the method comprising:// //
• determining the conductivity of the raw water by means of a conductivity sensor (12), and determining therefrom the total hardness of the raw water using a calibration characteristic stored in an electric control unit (11),
• determining the first partial volume flow V(t)partial1soft directly or indirectly using the at least one flow meter (13, 14, 17),
• deriving a total hardness I of the raw water which is used for controlling the regeneration process of the ion exchange resin (5), is from the measured conductivity by means of a first calibration characteristic (F1);// //
• deriving a total hardness II of the raw water used for controlling the admixing device from the measured conductivity by means of a second calibration characteristic (F2), wherein the second calibration characteristic (F2) is different from the first calibration characteristic (F1) and wherein the total hardness I derived from the first calibration characteristic (F1) is at least section-wise larger than the total hardness II derived from the second calibration characteristic (F2).