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. & ^# V$ _8 s: D& z% d( d- c
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Solution: turn off water supply and take the humidifier apart and clean it will stop the leaking.9 x: F. }& S" q% `
" Q- \ y0 C0 W2 [8 h+ Z 0 `- n- |! Y0 F; |Otherwise, find a professional or change a new set.