The MainGuard #78 Blow-Off installs underground in a standard meter box. Designed and engineered specifically for flushing, the #78 provides excellent flow rates for improving chlorine residual levels and flushing disinfection byproducts (DBPs) to keep water safe for consumers. Its unique valve design allows for a full clear-channel flow that is superior to other blow-offs for moving water and passing debris easily. The #78 is also designed to allow for throttling the flow of water while at the same time covering the drain hole to avoid unnecessary erosion. The MainGuard #78 comes standard with all brass principle working parts, a 2″ FIP vertical inlet, a 2 ½” NST outlet, and locking security cover. The #78 is self draining and non-freezing, and is fully serviceable from above ground. Certified to NSF/ANSI 372.