Abstract: An anti-backflow device for preventing fluids from flowing back into a water supply system. The device adapted for attaching to a connecting rod inside a sillcock tube of a standard antifreeze sillcock. The device held in an open position for allowing water to flow through the sillcock under normal operating conditions. The device automatically stopping the backflow of water in the sillcock should there be a loss of water pressure to the sillcock and preventing fluids such as insecticides, chemicals, or the like mixed with water from polluting the water system.