Siphon and backflow resistant valve

A vacuum breaker valve assembly located between a plumbing fitting and a water supply line for preventing backflow and siphoning conditions, the valve assembly comprising:

• a) a valve housing including a first end and a second end, the first end having an inlet orifice for receiving water into said housing from a supply source, the second end having an exit port for releasing water to a demand source;
• b) a substantially cylindrical valve chamber located within said valve housing, said chamber at least partially enclosed by an end wall and a cap assembly;
• c) a plurality of air apertures located in said end wall for allowing the passing of air into said chamber;
• d) a variable width diaphragm located within said chamber having:
• i) a first and a second portion, said first portion assuming a normally closed position by sealing said inlet orifice, said second portion assuming a normally closed position by sealing said air apertures;
• ii) an abutment portion that coacts with said cap assembly, the abutment for securing the diaphragm to said end wall;
• iii) a pair of lobes extending from said first portion;
• iv) a notch line located along said second portion providing enhanced flexing to said second portion between an open and closed position;
• and
• v) a projection extending from said first portion providing increased strength to the first portion when sealing said inlet orifice;
• e) a recess within said valve chamber for receiving and orienting said cap assembly;
• f) whereby a sub-atmospheric pressure within said supply line results in the flexing of the second portion along said notch line thereby displacing the second portion from said closed position to said open position allowing air to enter through said air apertures and sealing said first portion to an antibackflow position.