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. - m- I. j F' [$ R0 t* ~* h' d' I. o8 {7 c% [
Solution: turn off water supply and take the humidifier apart and clean it will stop the leaking.: O. ~( G n; G. A @9 Q' O
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Otherwise, find a professional or change a new set.