A new-style product developed by aiming at the defect for the existing slightly-resisted slowly-closed check valve not to be applicable for a sewage system and used at the outlet of pumps or in the water supply and drainage, fire-fighting and warming system's pipeline to act as a safety device to prevent the pump from back moving due to the water hammer impact caused by the back flow of the medium when the pump stops, the technical and economical features come as below:

•  For the water hammer eliminator, brand-new designed, reasonably structured and equipped with a slowly-closed device, able to prevent destructive water hammer, of a stable and reliable performance.

•  Stable movement without shock and noise, safe and reliable, long durable.

•  Good sealing effect, the sealing face is contacted with a rubber soft seal.

•  Anti-corrosion, longer duration by 5-7 times that of the swing type check valve.

•  Use an external hydraulic type and, different from the common slightly-resisted slowly-closed check valves, the slowly-closed device of it is outside placed instead of inside placed and, because of non-contact with the medium, the by-pass pipe will not be made blocked up and it is applicable for use in sewage medium with a good slowly-closed effect.