The Watts 0342692 Pressure Relief Valve (30 PSI, 3/4" MXF, M335M2) is a safety device designed to protect hydronic heating systems and boilers from excessive pressure buildup. It automatically releases pressure when system limits are exceeded, preventing damage to equipment and ensuring safe operation. https://www.partshnc.com/0342692-watts-m335m2-34-mxf-30-hotwtrrlfvl