The invention relates to a device for regenerating an ion exchange cartridge. In household appliances with an electric heating element for heating water, such as irons, coffee makers, and electric water kettles, deposition of scale is prevented by using an ion exchange cartridge (16) comprising a resin (23) which binds alkaline earth metal ions such as Ca?2+ and Mg2+¿, but also negative ions such as SO¿4?2- and CO¿3?2- ions. The device is a simple tool in which the cartridge can be inserted for regeneration. The device comprises a reservoir (2) with an outlet (10) to which an inlet (6) of the cartridge can be coupled. By filling the reservoir with a brine, for example 1 l of water with 10 % by weight of NaCl, said brine will flow through the cartridge replacing the alkaline earth metal ions, carbonate ions, and sulfate ions in the resin with the alkali metal ions (Na+) and the chloride ions (Cl-) of the brine. The brine can be easily drained into a sink.