Protective well for underground hydrant

The utility model relates to a protective cylinder for an underground fire hydrant. The disasters that a fire hydrant is flooded by water in summer and is frozen by the water in winter can be avoided. A steel cylinder 2 with a bottom 3 is arranged in a well provided with the fire hydrant 11. The lower part of the cylinder 2 is provided with an inlet of a water inlet pipe 10. A sealing ring 5 is arranged on the inlet. Groundwater can not infilter from the inlet. An upper cover of the cylinder 2 is a fastening cover 1. After the cover can be fastened, rain water can not enter the cylinder. A water stop sheet 6 and an insulating layer 7 are arranged in the inner part of the utility model. The fire hydrant can not be frozen in winter. Once the inner part of the utility model has accumulated water, the utility model is also provided with a measuring suction pipe 9 in order to extract the accumulated water. The common fire hydrant is stable, and the utility model immediately plays a role when used.