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.
1/4 inch Anti-Vacuum Valve
1/4″ Anti-Vacuum Valve with Long Pin allows oxygen to enter boilers until pressure builds up. For example, as the temperature rises in the boiler, the steam starts creating pressure. Once the pressure builds up, it starts to push the valve upwards and shuts it. Thus, allowing the boiler to pressurize.