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. $ }* r. ^7 i" t0 E4 j
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Solution: turn off water supply and take the humidifier apart and clean it will stop the leaking. ! [+ Y2 \9 u$ g) A% [& B( Z- E' v6 j: n) j; U
. C6 C4 j p$ S& h; t0 OOtherwise, find a professional or change a new set.