A dialysis monitor (100, 200, 300, 500) comprising: an inlet configured for receiving purified water supplied to the dialysis monitor from a water supply system; a treatment fluid path configured to provide treatment fluid to a dialyzer while dialysis treatment is being performed by the dialysis monitor; a controller; wherein: the dialysis monitor further comprises a tank connected to the treatment fluid path; and the dialysis monitor is configured to perform disinfection and/or cleaning of at least a portion of said treatment fluid path by means of a disinfection and/or cleaning fluid at a first disinfection and/or cleaning event; and the dialysis monitor is configured to store at least a portion of said used disinfection and/or cleaning fluid in said tank at the end of or after said first disinfection and/or cleaning event; and the dialysis monitor is configured to discharge at least a portion of said stored, used disinfection and/or cleaning fluid into at least of a portion of said treatment fluid path at a subsequent disinfection and/or cleaning event; and the dialysis monitor further comprises an actuator located at the treatment fluid path upstream of the connection of the treatment fluid path to the tank, and the controller is programmed to control the actuator to close the actuator at a time fluid is discharged from the tank to the treatment fluid path. an inlet configured for receiving purified water supplied to the dialysis monitor from a water supply system; a treatment fluid path configured to provide treatment fluid to a dialyzer while dialysis treatment is being performed by the dialysis monitor; a controller; wherein: the dialysis monitor further comprises a tank connected to the treatment fluid path; and the dialysis monitor is configured to perform disinfection and/or cleaning of at least a portion of said treatment fluid path by means of a disinfection and/or cleaning fluid at a first disinfection and/or cleaning event; and the dialysis monitor is configured to store at least a portion of said used disinfection and/or cleaning fluid in said tank at the end of or after said first disinfection and/or cleaning event; and the dialysis monitor is configured to discharge at least a portion of said stored, used disinfection and/or cleaning fluid into at least of a portion of said treatment fluid path at a subsequent disinfection and/or cleaning event; and the dialysis monitor further comprises an actuator located at the treatment fluid path upstream of the connection of the treatment fluid path to the tank, and the controller is programmed to control the actuator to close the actuator at a time fluid is discharged from the tank to the treatment fluid path. the dialysis monitor further comprises a tank connected to the treatment fluid path; and the dialysis monitor is configured to perform disinfection and/or cleaning of at least a portion of said treatment fluid path by means of a disinfection and/or cleaning fluid at a first disinfection and/or cleaning event; and the dialysis monitor is configured to store at least a portion of said used disinfection and/or cleaning fluid in said tank at the end of or after said first disinfection and/or cleaning event; and the dialysis monitor is configured to discharge at least a portion of said stored, used disinfection and/or cleaning fluid into at least of a portion of said treatment fluid path at a subsequent disinfection and/or cleaning event; and the dialysis monitor further comprises an actuator located at the treatment fluid path upstream of the connection of the treatment fluid path to the tank, and the controller is programmed to control the actuator to close the actuator at a time fluid is discharged from the tank to the treatment fluid path.