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. ; o' c1 N4 F& @' @8 x% N) j" T" V8 h: a5 I4 o( _% u
Solution: turn off water supply and take the humidifier apart and clean it will stop the leaking. + r2 K# E+ P- |2 V* `2 `1 {; ` 4 T; \. I" Z8 O; ]: D+ x: Z( p# z) ^8 F
Otherwise, find a professional or change a new set.