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. $ H7 g' q( I3 |; `0 p; a* U
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Solution: turn off water supply and take the humidifier apart and clean it will stop the leaking.) ~( r; r5 T# ]3 [' v
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5 R4 O) Z8 H' M8 \Otherwise, find a professional or change a new set.