Type - Water Service Vacuum Relief ValveSpecifications. . Allows air to enter a closed system to automatically relieve vacuum conditions that could suck water from the system, burn out a water heater, or collapse a tank. CSA, ANSI Massachusetts State Code Listings. Size: 1/2 in. Dimensions: 3 x 3 x 3 in. Item Weight: 0.5 lbs. Features: 1. 2...