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. $ c7 O" f# S/ K6 O6 s' {5 X3 q, A2 e: Z( I
Solution: turn off water supply and take the humidifier apart and clean it will stop the leaking. % s4 ~! k. h7 O! g4 s* |# b L3 d& `, S' k/ y; w( H
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Otherwise, find a professional or change a new set.