A fresh washing liquid tank and if required a dirty water tank are integrated in a housing (1). A suction nozzle (7) for dirty water is arranged behind the housing (1) at a fixed distance thereof, in its direction of motion. The suction nozzle (7) is connected by a suction hose (8) to a dirty water inlet of the housing (1). A dosing system (11) with a dosing and mixing device for cleaning product concentrate and water, a concentrate reservoir (12) linked to the dosing device and a water inlet (14) linked to the dosing device, is arranged between the housing (1) and the suction hose (8). The washing liquid may be accurately dosed. The time usually spent to fill the tank with the washing liquid is considerably reduced. The apparatus is compact, easy to steer, mobile and may be used without water supply and/or sewage connection.