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. 1 c+ |9 c6 f$ K1 I( r
8 A- W5 j0 p9 l; _7 m- O
Solution: turn off water supply and take the humidifier apart and clean it will stop the leaking. 4 n1 P/ ]) Q" M9 L0 f! c+ q# e1 Z% D9 x/ m4 U
$ ?' i ?$ `6 L# n
Otherwise, find a professional or change a new set.