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. & A% D( R/ S4 y9 u' s" g0 b( q4 ?; w! R0 A) O' c" \
Solution: turn off water supply and take the humidifier apart and clean it will stop the leaking. $ W# w. X( F5 J$ X8 I ; {3 d) B3 y* g6 w5 R+ H" X: ~7 `2 Q! x0 Y# F/ B$ X
Otherwise, find a professional or change a new set.