... harmful gas corrosion, and have an explosion protection function.3) used to filterOptional BLUEWATER control valves are as filters.4 ... ) used in hot water systemBLUEWATER control valves (6600, 6800, 7800, 8600, 8,800) are optional as hot water system (temperature ... device effluent pipeline, do not let without handle hard water system, the BLUEWATER control valves, all can choose no hard water ...