The Kärcher K 2 Classic is primarily designed for operation with a water connection. However, operation via a bucket or other water container is possible, provided a suitable suction hose with non-return valve is used. For use with a bucket, you will need the suction hose SH 5:
https://www.galaxus.ch/de/s4/product/kaercher-sh-5-hochdruckreiniger-zubehoer-2585449.
This is suitable for all Kärcher high-pressure cleaners in classes K 1 to K 7 and allows water to be drawn in from alternative sources such as rain barrels or water barrels. For more demanding cleaning work, however, we recommend a more powerful model from K 4.
Under the following link you will find all compatible models for the suction hose at the bottom:
https://s1.kaercher-media.com/documents...