I used to use a bypass system, with the "lever" valve. The reasons I now use a varistream are-
Constant, reliable flow- no matter how high or low the brush is.
Pump runs slower thus battery lasts a LOT longer.
Very accurate cut off.
Basically, once "set up & tuned" correctly- switch on & forget about it, your perfect flow & pressure, rock solid, day in day out. No running back to the van to alter anything!
