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. # p' F& O, K8 f0 k) d 3 q+ c' z5 X- @; W1 t0 T9 oSolution: turn off water supply and take the humidifier apart and clean it will stop the leaking. # p4 y6 x$ A# |: \- Q G7 i( `0 `* l# P" B- T/ H( N
$ O( L; L6 ~# J! J* o( H/ wOtherwise, find a professional or change a new set.