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. 4 P Z7 K& j$ J9 _$ c! I% p# @8 U + [; m& s/ i# D! }" USolution: turn off water supply and take the humidifier apart and clean it will stop the leaking. * h( D' M& k( j* D( N6 a- O' f% z 1 D6 N5 v5 H9 l/ A8 Z 6 m/ h% r/ L0 ? O3 u& L! `Otherwise, find a professional or change a new set.