How much water does my Aprilaire humidifier use?

Consumer question:

My unit seems to be dumping alot of water into the drain 3gals every 2 hrs. Is the metering valve adjustable at the locknut screw on the end of metering valve?

Aprilaires’ response:

Thank you for your email regarding your model 700 Aprilaire humidifier. The feed rate of your model 700 is 6 gallons per hour(GPH). The evaporation rate is .75 GPH. If the humidifier were to run a solid hour it would evaporate .75 GPH and the remaining 5.25 GPH is used to flush away the minerals left behind from the evaporation process. Based on the operation we described above and your email it appears your model 700 is operating properly.

5 thoughts on “How much water does my Aprilaire humidifier use?

  1. Gary

    Should there be a steady stream of water coming out the drain hose while the humidifier is running? My floor drain can’t handle the amount of water coming through. Not sure if this is a normal amount? It is a 600 model and it overflowed a plastic keg barrel overnight at the 5 setting. Probably 15-20 gallons or so.

  2. brad

    Thank you for your inquiry regarding the water usage of your model 600 Aprilaire humidifier. Your model 600 is a drain through humidifier. This means anytime the humidifier is operating , water will be draining from the unit. The feed rate for your model 600 is 3 gallons per hour(GPH). We evaporate .70 GPH and the remaining 2.3 gallons is drained away. If the humidifier was to operate for 8 hours, 18 gallons would be drained. This is normal and necessary as if less water was supplied to the humidifier, the result would be less humidity created.

    Thank you for giving us the opportunity to be of assistance.

  3. Greg

    If there is no call for humidity from the humidistat, does the water usage drop to zero, or is there some level of constant flow used to maintain moisture inside? (ie. Does it only use water during operation cycles, or is there any sort of continuous demand regardless of level of usage?)

  4. Mark

    I have the Aprilaire 600M. I just installed and it is draining at a rate of 4.3 gallons per hour. I used a measuring cup and got a quart every 3.5 minutes, I believe this translates to 4.3 gallons per hour. As the unit is a 3 gallon per hour model, do I have a problem or something?

    1. aprilaireadmin

      Hi Mark,

      Thank you for the email re4garding the Aprilaire model 600M humidifier.

      Your calculations are correct. I would ensure that the yellow orifice, installed in the feed tube, at the solenoid valve end is not damaged. It is possible that the yellow orifice in the feed tube may need replaced to get the flow rate back to the normal 3 gal/hr.


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