The 4-Way Brass Mixing Valve 721 is used to mix supply water from a hydronic source with water returning from a system. It is designed for use in either closed loop or open loop hydronic systems. This 4-way valve has standard female NPT threads, as well as a maximum leak through rate of 1 percent to allow for water expansion during temperature changes. The valve position can be manually set using the handle. An Actuating Motor 741 can be used to automatically operate the valve.