A water lance blower for cleaning heat installations includes a water lance moveably mounted with a mouth thereof at or in a hatch. The water lance can blow a jet of water through the heating installation, through which flames and/or flue gases are guided, to wall regions accessible from the hatch, during operation. The water lance is provided with at least one sensor for detecting at least one predeterminable measurement value for monitoring the quality of the water jet. A method for operating the water lance blower includes detecting and evaluating at least one parameter characteristic of the quality of the water jet as a measurement value during operation of the water lance blower. The method permits an evaluation of the cleaning effect of the water lance blower during operation and, if required, influencing of the same.