900X is an emergency shut-off valve for fire water and living water supply system in parallel, to the direction of the water supply valve deployment. When a fire occurs, the fire needed a lot of water, living water immediately cut off to ensure adequate fire water; when the fire stopped the water pressure decreases, the valve automatically opens, showing a normally open state, restore domestic water supply. The valve allows the system without a separate dedicated fire alone water supply network, greatly saving construction costs and water consumption. Valve control high sensitivity, safe, reliable, and easy to debug, long life