A water cleaner comprising a hydraulic circuit equipped with: - a pump unit arranged to feed a predetermined flow rate of a cleaning liquid into a main branch of said hydraulic circuit; - a boiler arranged to provide a predetermined thermal power to at least a part of said predetermined flow rate of said cleaning liquid fed into said boiler in order to cause the flow rate to be heated from an inlet temperature (Ti) up to a predetermined outlet temperature (Tu*); - a delivery device hydraulically connected to said boiler and arranged to deliver said flow rate of said cleaning liquid fed into said boiler at said predetermined outlet temperature (Tu*); - an adjustment device configured to adjust said determined cleaning liquid flow rate fed into said boiler; a second temperature sensor arranged to detect the temperature of said cleaning liquid flow rate downstream of said boiler and to generate a corresponding outlet temperature signal (Tu); - a control unit operatively connected to said second temperature sensor and to said adjustment device, T said water cleaner being characterized in that it comprises, furthermore: - a first temperature sensor arranged to detect the temperature of said cleaning liquid flow rate upstream of said boiler and to generate a corresponding inlet temperature signal (Ti); - the control unit operatively connected to said first temperature sensor, to said second temperature sensor and to said adjustment device, said control unit being configured to set a determined starting flow rate of said cleaning liquid to be fed into said boiler depending on said inlet temperature signal (Ti) received from said first sensor, to compare said outlet temperature signal (Tu) received by said second temperature sensor with said predetermined value of the outlet temperature (Tu*), and to operate said adjustment device to increase, or decrease, with respect to said starting flow rate said flow rate of said cleaning liquid fed into said boiler if said outlet temperature signal (Tu) is different from said predetermined outlet temperature value (Tu*). - a pump unit arranged to feed a predetermined flow rate of a cleaning liquid into a main branch of said hydraulic circuit; - a boiler arranged to provide a predetermined thermal power to at least a part of said predetermined flow rate of said cleaning liquid fed into said boiler in order to cause the flow rate to be heated from an inlet temperature (Ti) up to a predetermined outlet temperature (Tu*); - a delivery device hydraulically connected to said boiler and arranged to deliver said flow rate of said cleaning liquid fed into said boiler at said predetermined outlet temperature (Tu*); - an adjustment device configured to adjust said determined cleaning liquid flow rate fed into said boiler; - a control unit operatively connected to said second temperature sensor and to said adjustment device, T - a first temperature sensor arranged to detect the temperature of said cleaning liquid flow rate upstream of said boiler and to generate a corresponding inlet temperature signal (Ti); - the control unit operatively connected to said first temperature sensor, to said second temperature sensor and to said adjustment device, said control unit being configured to set a determined starting flow rate of said cleaning liquid to be fed into said boiler depending on said inlet temperature signal (Ti) received from said first sensor, to compare said outlet temperature signal (Tu) received by said second temperature sensor with said predetermined value of the outlet temperature (Tu*), and to operate said adjustment device to increase, or decrease, with respect to said starting flow rate said flow rate of said cleaning liquid fed into said boiler if said outlet temperature signal (Tu) is different from said predetermined outlet temperature value (Tu*).