Patent ID: 8302623

Claim:
An anti-backflow device for an outflow nozzle of a fire hydrant, comprising: a) a hollow cylindrical insert defining an interior, said insert having an external surface, an interior surface, a front end, a rear end, a top portion, and a bottom portion; b) a curved anti-backflow flap having a hinge at one end and an inflow fin at an opposite end; c) said flap being hinged rotatably within the insert to the interior surface and top portion of the insert, near the rear end of the insert, so that outflow of water from the fire hydrant will cause the flap to rotate towards the front end and top portion of the insert; d) a curved flap seal on the interior surface of the insert near the rear end of the insert, said curved flap seal reversibly engaging a perimeter of the flap, thereby reversibly closing the rear end of the insert; and e) an anti-tamper protrusion on the interior surface of said insert to prevent the insertion of a tool or device into said insert and under said flap to force said flap into a fixed open position.