It is possible that the shut-off valve was blocked by the cumulated white stuff. As a result, water supply can not be stopped even when water level is high. - A3 v5 G* h! w! d. P7 g
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Solution: turn off water supply and take the humidifier apart and clean it will stop the leaking.5 w/ Q) Q0 E1 o* E
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Otherwise, find a professional or change a new set.