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. 5 n3 g8 N k3 @; s8 c- ?1 K $ ]2 R$ r, h/ _' gSolution: turn off water supply and take the humidifier apart and clean it will stop the leaking. 4 M R1 }9 E+ g7 h6 |& v& S, J + U1 {. A d0 I/ S 7 f% {. a7 d/ k/ R% D* h" YOtherwise, find a professional or change a new set.