Also called siphon, anti-siphon or vacuum breaker valve. This valve allows air to escape the boiler as the water heats up, hissing and then closing off when the boiler water reaches it's operating temperature, sealed by the steam pressure created. Measure your existing valve: the outside of the male threads of a 1/4" BSP fitting measure 1/2". One may also use part W_517.

While it is recommended to install this valve in a vertical orientation (as pictured) it can and will function in a horizontal position.

Gaskets are not always required; as the valve and boiler expand any small leaks at the junction will likely disappear forever. A good rule of thumb: if your valve and boiler had a gasket, get a new replacement for added assurance.

Stainless steel made available as of 06/01/2019.

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