I have a proper lance and bottle mate and empty the washer after use every time. I've mixed with warm water before. It is the C120-3 I have. I also bought a little Karcher 2.14 that I use a 20l tank gravity fed to the Karcher to get around the preposterous and pointless hosepipe ban. In some ways I actually prefer the little Karcher as it is less powerful and more compact so I can be more accurate with the lance, get into panel gaps a lot more accurately as the spray pattern is more compact and not be scared of destroying paintwork rather than cleaning it. I think next time though I'm going to go for a more expensive washer, spend a good few quid and forget as this is the 3rd warranty replacement C120 I've had. They really don't like being worked too hard (and I don't work mine hard at all!!) It has plenty of breaks and not used constantly and it is always fed with a good water supply before pressurizing.