The Watts 0382328 740-3/4-50 A pressure relief valve for hydronic heating systems is the 1,352,000 Relief Valve. It safeguards the system by automatically releasing excess pressure that might break components or cause leaks. The valve can produce 1,352,000 BTU at a maximum pressure of 50 psi and includes a 3/4-inch female pipe thread connection. https://www.partshnc.com/0382328-watts-740-34-50-1352000-relf-vlv