The Spirovent Junior provides reliable automatic air release in the top of a hydronic system, allowing rapid filling and draining. When you use a Spirovent, no other air bleeders are needed. Use a Spirovent on every new hot- and/or chilled- water system for air related problems in existing systems. It's a simple retrofit. Just locate the Spirovent in the common piping at the boiler. This is the point where the water is the hottest. The Spirovent Junior comes in 3/4", 1", 1-1/4" , and 1-1/2" female-threaded sizes and is made of solid brass for long life. The 1" and 1-1/4" models are tapped at the bottom to accommodate a bladder type compression tank.