To overcome a problem such that a thunk, which makes a person very uneasy, is generated by a transfer of an impact to a floor via a toilet bowl because the impact is made as in the case of a water hammer phenomenon by having a drain valve of a toilet bowl flushing tank device closed by a strong force. 便器洗浄タンク装置の排水弁が強い力で閉止されることにより、ウォーターハンマーの現象に類似して衝撃が発生するため、該衝撃が便器を経由して床に伝わってズシーンという、人を非常に不安にさせる音が発生してしまう。 - 特許庁