Device characteristics 4-way rotary mixing valve is made of brass. It is equipped with the knob for manual adjustment. 4-way ARV valves are used as mixing valves, with simultaneous increase of the return temperature from the system in boilers for solid fuels. The readable scale indicated on the knob lid allows precise determination of the degree of valve opening. The bold element of the knob circuit reflects the position of the speculum inside the valve. Each valve is supplied with two lids having the following scale: one with the graduation “from 0 to 10”, second with the graduation “from 10 to 0”. This facilitates setting and reading of the degree of the valve opening in different installation positions. ARV valves cooperate with ARM actuators with the rotation angle of 90 degrees, which enables the automation of their operation. They can be used in systems with clean water or water containing up to 50% glycol.