Question about Emerson HDC12 Humidifier

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Left Tank won't empty

I just bought an Emerson HDC12 recently. I have made sure the unit is level front to back and left to right. I have filled both tanks with water and run it successfully until the F light lites up telling me to refill my humidifier. However the left tank stays full and never loses any water at all. I have switched the plungers between the tanks, I noticed the post for the left plunger is much lower so I stuck a spacer on the bottom of the plunger to offset the difference between the tanks, and lastly I am now trying the empty humidifier position. (Tying the float up stuck in the on position.) I won't know if this works until that right tank empties again. I can let water out of the left tank if I push up on the plunger so it is not geetting stuck in there by vacumn (I think). This unit is supposed to drain the right tank before the left but I thought they both were supposed to drain before the float fell enough to shut off the humidifier. Anybody have any ideas on what to try next? Thanks

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  • Tom Chappell Mar 12, 2007

    Sorry everyone this unit is a Moistair 14 gallon per day unit. The HDC12 is the model of filter it uses so someone messed up early on.
    Since no one at Emerson ever tried to help I ended up switching the right and left tanks around. The left I put on the right side and the right tank I put on the left side. If I move them around a little I can get them to actually work. This doesn't work when they are on the correct sides though. Also noted that even though the float is at the empty whole unit of water (End of season setting) the unti still shuts off when the tanks are empty but there is still water in the bottom so even that float doesn't work.
    I may just return this unit and tell them it is a piece of crud. For $149 you would at least think the humidifier would work as advertised. I shouldn't have to jury rig the thing to get it to work.

  • deano1575 Jan 26, 2008

    I have the exact same problem with the MoiostAir HD13050. And I have tried the same things that tomc1965 has done.

  • Anonymous Nov 11, 2008

    I just bought the same unit and I am having the same problem. My parents have had this unit for 2 years and have not had this problem. I am planning on retuning it .

  • Gizmoman Jan 19, 2009

    Same problem, however my unit has worked fine for about five years, This problem has only recently surfaced. Very perplexing!!



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Eureka! Solved my "left bottle not emptying" problem. The problem was not with the bottle but that the top of unit which houses the on/off switch was not seated properly. It takes only a very slight difference in water level for the float to activate the switch, therefore if the top is raised even 1/4" the unit will shut off before the water level is low enough to allow the left bottle to drain.

Posted on Jan 20, 2009

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I had the same problem from day 1 with my MoistAir HD14070.
I inserted a piece of 4' square ceramic tile under each front wheel. This raised the front slightly more (unit is setting on carpeted floor) and gave the unit a more firm base to sit on. Works like a charm now.
Hope this helps someone.

Posted on Jan 05, 2010


I've had the same problem. My solution has been to remove the plunger on the left tank. (Kind of defeats the purpose of changing the tanks without spilling water all over the place.) I really like the humidifier and this problem is minor compared with other humidifiers I've had in the past.

Posted on Mar 19, 2008

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The problem is more than likely due to a calcium and mineral build up in the tank and the tubing.
Hopefully, it's not to late to do something about it. So follow the instructions below,

Unplug the unit.

Remove any remaining water from the tank.

Mix a 50/50 solution of White Distilled Vinegar and Bottled Distilled Water (enough to fill the tank) and pour the solution into the tank. Allow t to sit overnight. In the morning, plug the unit in and turn it ON. If it doesn't start producing steam, turn the unit OFF, unplug it and empty the tank. Mix more solution as described above, pour it in the tank and allow it to set for 3 or more hours. The plug the unit in and turn it ON. Hopefully, this time, it will start to produce steam. If it does allow it to run until the tank is half empty. Turn the unit OFf and empty the remaining solution from the tank. Refill the the tank with Bottled Distilled Water and run the unit until it's empty. That will flush the system.

In the future, I would highly recommend the use of Bottled Distilled Water, rather than using tap water.

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The unit may simply has a calcium scale build up and it's blocking the water passage. To clean it, empty in water remaining in the tank. Mix a 50/50 solution of White Vinegar and Bottled Distilled Water and fill the tank. Allow it to soak for at least one hour, then turn the unit ON. Place you hand in front of the misting nozzle to see if it's working. If you don't feel any mist, turn the unit OFF and allow it sit over night. If you do feel mist, allow it to run until the tank is 3/4's empty Turn the unit OFF, pour out the remaining solution and refill with Bottled Distilled Water. Run the humidifier until it's empty. This will flush the system entirely. In the future, I would recommend you use Bottled Distilled Water, instead of Tap Water. If you do, you won't have to descale the unit any more.

Hope this helped you, please let me know. Thanks.

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I turn the humidifier on l or ll. The light is grean but it is not releasing steam or anything. I don't hear a noise and the water level stays the same.

The humidifier may be clogged with a calcium scale build up. Especially, if you use well water or your municipal water supply has a high chemical content.

To solve this problem do the following. Mix a 50/50 solution of White Vinegar and Bottled Distilled Water (enough to fill the tank). Empty any water that is currently in the tank and fill it with the 50/50 solution. Allow at least one hour, before turning the unit ON. After turning it ON place you hand in front of the mist nozzle to see if any mist is being generated. If it's generating mist, allow it to run until the tank is 3/4's empty. Then turn the unit OFF, unplug it and empty the remaining solution. Refill with Bottled Distilled Water and run until the tank is empty.

If the unit did not produce mist after one hour of soaking, allow it to set over night and then follow the procedure above. Generally, an overnight soaking will do the trick. In the future, I recommend using Bottle Distilled Water rather than your tap water.

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If the unit is on carpet, use the caster feet supplied with the unit. The weight of the bottles causes the front of the unit to be lower than the back. This prevents the sensor from switching bottles, causing the left bottle not to empty. The caster feet keep the water sufficiently level for the sensor to work.

Here is another thread on the matter.

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It means Change Filter.

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Located My Manual:
Hope this helps!

1. Remove tank from base. Turn upside down and unscrew filling cap. Fill tank with clean, cool, distilled, or tap water. Water temp should NEVER be too hot or too cold. Return tank to base and let sit for a few minutes. Be sure the filling cap of the tank is tightened firmly.

2. Plug power cord into a 110-120V AC wall outlet only. Turn power switch to "on" position. Power light will illuminate. Turn mist nozzle until desired level is being released. Aim nozzle away from furniture and walls.

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Place unit on level surface away from direct sunlight.

Mild bleach and water solution for cleaning, never detergent.
Clean every 3rd day during use. Clean after long storage
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