You can use a normal garden hose to supply water to the Kärcher K4. There is no fixed maximum hose length. However, for very long hoses (e.g. 40 m or more), we recommend a hose with a larger diameter, ideally 3/4", so that sufficient water flow and pressure reaches the appliance. With a 1/2" hose, the pressure can already drop noticeably at this length. A constant water supply and a maximum inlet temperature of 40 °C are also important.
The Surface Cleaner T 350 is not typically included with the Kärcher K4 Silent Home (CH version, Electrical connection) pressure washer. The standard package usually includes the pressure washer unit, a high-pressure hose, a spray lance, and a detergent suction tube, among other basic accessories. For specific details on what is included, it is best to refer to the manufacturer's official packaging list or the product description provided by the retailer.