A water cleaner comprising: - a pump unit arranged to feed a determined flow of a cleaning liquid at a predetermined pressure in a hydraulic circuit; - a boiler arranged to supply to said cleaning liquid a predetermined thermal power in order to cause it to heat up to a predetermined temperature, said boiler being provided with an outlet section for said cleaning liquid having a predetermined diameter; - a delivery device hydraulically connected to said outlet section of said boiler and arranged to deliver said flow of said cleaning liquid at said predetermined pressure and at said predetermined temperature; wherein said water cleaner provides, furthermore: - an adjusting unit arranged to adjust said thermal power transferred by said boiler to said cleaning liquid, said adjusting unit comprising: - a temperature sensor, which is arranged to be dipped, in use, in said high pressure cleaning liquid, in such a way to detect its temperature and generate a corresponding signal of temperature Ti; - a control unit operatively connected to said temperature sensor, said control unit comprising a microprocessor and arranged to increase, or decrease, said thermal power transferred by said boiler to said cleaning liquid, in function of said signal of temperature Ti received by said temperature sensor; - a measurement block provided with a housing arranged to house, in use, said temperature sensor, said measurement block having an inlet mouth for the inlet of said cleaning liquid, and an outlet mouth for the exit of said cleaning liquid, between said inlet mouth and said outlet mouth a passageway, which is hydraulically connected to said housing, being defined through which, in use, said cleaning liquid is arranged to flow, said measurement block being made of a single metallic material having a predetermined thermal conductivity, being configured in such a way that said temperature sensor is positioned, in use, at a distance d less than 20 mm from an outlet mouth of said outlet section of said boiler, and in such a way that the section Φ of passageway where the cleaning liquid reaches said temperature sensor, has a surface higher than 100 mm 2, in such a way to obtain a highly accurate temperature detection by said temperature sensor immediately downstream of said boiler. - a pump unit arranged to feed a determined flow of a cleaning liquid at a predetermined pressure in a hydraulic circuit; - a boiler arranged to supply to said cleaning liquid a predetermined thermal power in order to cause it to heat up to a predetermined temperature, said boiler being provided with an outlet section for said cleaning liquid having a predetermined diameter; - a delivery device hydraulically connected to said outlet section of said boiler and arranged to deliver said flow of said cleaning liquid at said predetermined pressure and at said predetermined temperature; - an adjusting unit arranged to adjust said thermal power transferred by said boiler to said cleaning liquid, said adjusting unit comprising: - a temperature sensor, which is arranged to be dipped, in use, in said high pressure cleaning liquid, in such a way to detect its temperature and generate a corresponding signal of temperature Ti; - a control unit operatively connected to said temperature sensor, said control unit comprising a microprocessor and arranged to increase, or decrease, said thermal power transferred by said boiler to said cleaning liquid, in function of said signal of temperature Ti received by said temperature sensor; - a temperature sensor, which is arranged to be dipped, in use, in said high pressure cleaning liquid, in such a way to detect its temperature and generate a corresponding signal of temperature Ti; - a control unit operatively connected to said temperature sensor, said control unit comprising a microprocessor and arranged to increase, or decrease, said thermal power transferred by said boiler to said cleaning liquid, in function of said signal of temperature Ti received by said temperature sensor; - a measurement block provided with a housing arranged to house, in use, said temperature sensor, said measurement block having an inlet mouth for the inlet of said cleaning liquid, and an outlet mouth for the exit of said cleaning liquid, between said inlet mouth and said outlet mouth a passageway, which is hydraulically connected to said housing, being defined through which, in use, said cleaning liquid is arranged to flow, said measurement block being made of a single metallic material having a predetermined thermal conductivity, being configured in such a way that said temperature sensor is positioned, in use, at a distance d less than 20 mm from an outlet mouth of said outlet section of said boiler, and in such a way that the section Φ of passageway where the cleaning liquid reaches said temperature sensor, has a surface higher than 100 mm 2, in such a way to obtain a highly accurate temperature detection by said temperature sensor immediately downstream of said boiler.