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. ! l, ^# x5 A+ H
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Solution: turn off water supply and take the humidifier apart and clean it will stop the leaking. # \0 s- }7 S2 B1 @ 7 W7 q2 ^$ e; R8 [7 A5 E+ t4 D& q8 p/ |+ m" I8 V* ?
Otherwise, find a professional or change a new set.