Rancilio - Boiler Vacuum-Breaker Valve (3/8M)
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3/8M (metric) anti-syphon valve for Rancilio commercial espresso machines. Fits almost all other commercial machines. Part # RA10.060.051.Also known as a vacuum breaker valve, this important little device equalizes the air pressure in your boiler as it cools down and the pressure reverts to 1 BAR (atmosphere). This prevents the possibility of milk being sucked into the boiler inadvertently through the milk wands/valves. This happens more often than you think and results in costly boiler cleaning to remove the scorched milk smell.The screw-on brass weight on top of the valve should be removed when installed on commercial machines with smaller boilers (compact 2-groups and less), as the pressure inside the boiler will not be strong enough to fully-seal the valve unless the extra weight is removed. This extra weight is needed to ensure the anti-syphon/vacuum breaker valve does not close prematurely on larger boiler commercial espresso machines.Technicians Tip: Push in once a month, to ensure it does not stick in the closed position. This is very important in cases where the machine is always left on. If steam continuosly hisses from this valve, then the seal inside has hardened and the valve needs to be replaced.Metric "3/8" size actually measures about 5/8 inch across. Many older machines (pre 1990) such as the Rancilio Z series didn't have proper vacuum breakers (they used a ball bearing in the steam valve), but have an unused 3/8 plug on the boiler. Install one of these new valves for improved performance.