About hot and cold boosting pump,the rotating parts are in the clearn water. It solves the problem of inadequate water causing no lit fire because when the tap water is of low pressure .Three positions on the junction switch: WG series for function regulating. "O" for off, " I " for manual mode &, " II "for auto mode. Mainly used for pressurizing of cold/hot fresh water, home water use. It should not exceed 75℃ when using cold water type boosting pump.