The part(s) or condition(s) listed below for the symptom Humidifier overflowing are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.
Normally, once the environment reaches the proper level of humidity, the humidistat turns off, cutting power to the water inlet valve. If the humidstat turns off but the water inlet valve still doesn’t close, the valve might be stuck open. To determine if the water inlet valve is stuck open, disconnect the power to the humidifier and see if water still flows through the valve. If water flows through the water inlet valve even when the valve isn’t getting power, the valve is stuck open. If the valve is stuck, replace it. Water inlet valves are not repairable—if the water inlet valve is defective, you must replace it.
If the reservoir overfills the float valve might not be shutting off properly. When the float is lifted it should stop letting water into the reservoir. If water continues to flow then the float valve is likely stuck or jammed open and should be replaced.