A dialysis device comprising a dialysis circuit for providing dialysis fluid and returning purified fluid to the dialysis circuit. The device comprises an evaporator/condenser device, provided with an evaporator bag and a condenser bag. The evaporator bag receives dialysis fluid from the dialysis bag and produces steam, whereby a concentrated dialysis fluid is left and drained to a drain bag. The condenser bag receives the steam produced in the evaporation bag and condenses the steam for producing pure water for being returned to said dialysis circuit. The evaporation and condensation takes place at a subatmospheric pressure, such as between 30 and 70 mmHg at a temperature of about 30 to 44° C. Heat energy is provided to the evaporation bag and the condenser bag is cooled. The cooled energy may be absorbed by a heat pump for delivery of heat to the evaporator bag.
