The 5000 Series Taco Mixing Valve is a dual-purpose mixing or diverting valve that delivers fail-safe security and superior performance. Mixing Valves are a key component to hydronic heating systems. The Taco Mixing Valves work well in standard heating systems or Radiant Heat Systems. The Taco Mixing Valves come in several different sizes, with sweat connections. Taco makes several lines of hydronic heating valves including these mixing valves, zone valves, and air valves.