Underground hydrant is an outdoor ground fire water supply facilities. Used to supply water and fire water cannons, or directly connected to fire, the fire water supply is essential for outdoor facilities. Installation of underground, do not affect city, city. From a fire hydrant pipe bending ontology, outdoor, disc, seat and drain valve, the valve stem and interface components. Underground mines, city, is the fire-hydrant warehouse, dock, station, housing and public places of fire water supply necessary. Especially the area city and channel to furnish less is more. The product structure, reliable performance, convenient use.