This humdifier is a poorly engineered unit with lousy quality control. I bought four of these units. All four of them suffered from the well documented problem of the tanks not emptying properly. Not only is this extremely frustrating, but it defeats the whole purpose of purchasing a humidifier in the first place. My family would wake up in the morning with nose bleeds and sinus congestion because the unit would turn off in the middle of the night. Even though the tanks were full, the unit could not properly detect this and would shut off.
I work from home, so during the day when the units would constantly shut off, I would reposotion the tanks, the motor unit, and even the filter to no avail. I should also mention one of the four units had the fan motor burn out in less than two days which is absolutely ridiculous!!!
The build quality of the unit is very cheap. The tanks are made of thin blow-molded plastic. The unit is also very loud.
I WOULD ESPECIALLY LIKE TO NOTE THAT A LARGE AMOUNT OF THE POSITIVE REVIEWS ON THIS UNIT ARE BY PEOPLE WHO WERE GIVEN THIS UNIT FOR FREE. READ THE OTHER REVIEWS HERE AND ON OTHER WEBSITES AND AVOID THIS UNIT!!!!
I ended up purchasing the HCM-6009 instead, and I love them!!! They are a much higher quality unit than the 680. The 6009 has the same coverage area, features (minus the top fill feauture), and even take the same filters. The 6009 is sturdier, has wheels so you can move it around easier, and is quiter than the 680. MOST IMPORTANTLY IT ACTUALLY WORKS PROPERLY. BOTH TANKS DRAIN PROPERLY AND THE 6009 DOES A GREAT JOB HUMIDIFING OUR HOME.