There are two different styles of vacuum breakers: old and new. The model numbers for old style Sloan vacuum breakers begin with ‘V-500’. New style Sloan vacuum breaker model numbers start with ‘V-600’. Although 500 (old style) and 600 (new style) models are in fact interchangeable, there are subtle, yet very important difference between these models.
New style 600 version vacuum breaker repair kits contain vacuum breakers constructed of Permex – a durable synthetic rubber that can last up to four times longer than regular rubber. The specially designed tri-wing shape is now recessed up into the rubber sleeve. They have a straight sleeve shape, whereas the old-style rubber inserts had a duck-bill shape. Modern low-flow toilets and urinals create more back-pressure than older fixtures. This pressure is what causes most vacuum breaker leaks. Old style vacuum breakers are not designed to handle the back-pressure of newer low-flow fixtures. The careful design of the shape of the new-style vacuum breakers is what helps stop increased back pressure from causing leaks in low-flow units.