Many damages to water air valves have been reported in the past earthquakes, but the cause of the damage has not been clarified. Therefore, in order to investigate the actual condition and its cause of water air valves damaged by the 2016 Kumamoto Earthquake, we conducted a questionnaire survey on the damage to water air valves of waterworks bureaus in Kyushu region, and analyzed the damage factors of water air valves in Kumamoto City. As the results, it was confirmed that abrupt water pressure

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... change occurring immediately after the earthquake had a great influence on these damage. As the mechanism of abrupt water pressure change, the water hammer occurs by aeration in the air valve which is caused by dynamic pressure at deformed pipe etc. As a result, the air valve can be damaged.