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 at a first temperature to a dialyzer while dialysis treatment is being performed by the dialysis monitor; wherein said treatment fluid path comprises an inlet valve connected to said inlet; a controller; wherein: the dialysis monitor further comprises a tank connected to the treatment fluid path; and the tank is configured to hold a fluid having a temperature higher than said first temperature; wherein said controller is programmed to arrange that said tank holds said fluid having said higher temperature at least for a period of time when said treatment fluid path is supplying treatment fluid at said first temperature during a dialysis treatment; and wherein the dialysis monitor is configured to discharge the fluid held in the tank at a time when dialysis treatment is not being performed in order to perform thermal disinfection of at least a portion of said treatment fluid path; and wherein said controller is programmed to set said inlet valve in a fluidly closed state at the time of said thermal disinfection. 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 at a first temperature to a dialyzer while dialysis treatment is being performed by the dialysis monitor; wherein said treatment fluid path comprises an inlet valve connected to said inlet; a controller; wherein: the dialysis monitor further comprises a tank connected to the treatment fluid path; and the tank is configured to hold a fluid having a temperature higher than said first temperature; wherein said controller is programmed to arrange that said tank holds said fluid having said higher temperature at least for a period of time when said treatment fluid path is supplying treatment fluid at said first temperature during a dialysis treatment; and wherein the dialysis monitor is configured to discharge the fluid held in the tank at a time when dialysis treatment is not being performed in order to perform thermal disinfection of at least a portion of said treatment fluid path; and wherein said controller is programmed to set said inlet valve in a fluidly closed state at the time of said thermal disinfection. the dialysis monitor further comprises a tank connected to the treatment fluid path; and the tank is configured to hold a fluid having a temperature higher than said first temperature; wherein said controller is programmed to arrange that said tank holds said fluid having said higher temperature at least for a period of time when said treatment fluid path is supplying treatment fluid at said first temperature during a dialysis treatment; and wherein the dialysis monitor is configured to discharge the fluid held in the tank at a time when dialysis treatment is not being performed in order to perform thermal disinfection of at least a portion of said treatment fluid path; and wherein said controller is programmed to set said inlet valve in a fluidly closed state at the time of said thermal disinfection.