The wand which comes with the Prowler has a bypass fitted. The bypass helps prevent it bypassing when no water is passing through the pump, as with any truckmount. It is not totally nescessary but does help to preserve water. There is also a bypass on the outlet side of the machine which can be cranked open a little if using a non-bypass wand or handtool. This ensures a flow of water through the pump at all times preventing it overheating.