Watts 0004434 Valve The compact Relay in a Box design facilitates The compact Relay in a Box design facilitates rapid installation on the exterior of air handlers or pumping stations where moisture and dust ingress are concerns Its washable design allows for repeated service cycles—simply rinse with water and a mild detergent to restore its internal capture capacity without compromising structural integrity whereas the 100XL typically fits 3 4 inch connections and supports significantly higher BTU ratings this bronze body relief valve features a 4 inch extension thermostat with a specialized thermo bonded coating to resist mineral buildup and ensure consistent thermal response