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. |' `. j- S+ H5 R6 T0 n. H J+ A6 h
Solution: turn off water supply and take the humidifier apart and clean it will stop the leaking., [4 S5 y9 k& o9 q I
/ E* m' a/ I6 K$ }* T, l5 c0 d$ x) _3 o6 N
Otherwise, find a professional or change a new set.