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. 4 E6 _7 s( d7 M2 s: Z0 C( \8 L3 C
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Solution: turn off water supply and take the humidifier apart and clean it will stop the leaking. * V/ U! ?7 m8 m1 E% Z2 o' ^+ G $ h$ r1 e8 Y- t% W* q: F3 p- A, V+ p! B6 P0 l' q
Otherwise, find a professional or change a new set.