Aprilaire 500M - Bypass Humidifier 12 GPD with Manual Humidistat

The Aprilaire 500M ByPass FlowThru Whole House Humidifier with Manual Control humidifies up to 3,000 sq feet and disperses 17 gallons per day.

The Aprilaire 500M Flow-Thru Bypass Whole House Humidifier with manual control is perfect for adding comfort to your home during the dry winter months. The Aprilaire 500M is designed for use in small to midsized homes, efficiently humidifying up to 3,000 square feet and dispersing up to 12 gallons of water per day.


This bypass unit mounts directly to the duct of your heating and cooling system, allowing the humidity to be placed directly into the airflow and distributed evenly throughout the home.


Mounted on the supply or return duct (plenum), the unit is also easily reversible for right or left hand installation. Additionally, this model connects to a water line so you don't need to worry about filling it multiple times a day.  


Benefits of Evaporative Humidification: 

  • Prevents Flu and Allergies
  • Neutralizes Static Electricity
  • Reduces Pet Dander and Discomfort
  • Protects Fine Furniture, Wood Floors, and Musical Instruments
  • Relieves Dry Skin and Scratchy Throats
  • Reduces Heating Costs 


The Aprilaire 500M bypass humidifier is a manual humidifier, meaning this unit does not come with a digital, automatic humidistat like the Aprilaire 500A Unit. It comes standard with an Aprilaire4655 manual humidistat that can be wall or duct mounted on the return plenum of your unit. With this humidistat you will need to manually set and change the humidifier settings with any changes in the weather.


The Aprilaire 500M Humidifier is Shipped to you as a Complete System that Includes:



This Aprilaire 500M humidifier requires a plenum opening of 9-1/2" W by 9-1/2" H.  For electrical reference, this unit operates on 24 Volts at 60Hz with a .5 AMP requirement.

*Important note: If the Aprilaire bypass 500M humidifier is installed on a heat pump system it is best to hook the unit up to a hot water line. 


Aprilaire recommends a #4792 maintenance kit be used each humidification season to ensure that your 500M humidifier is operating optimally. Furthermore, using a genuine Aprilaire #10 water panel is highly suggested. This water panel was designed specifically for the Aprilaire 500M humidifier and provides the most comfortable and efficient output. Don't trust the aftermarket products to provide the same quality and overall experience as the genuine #10 Aprilaire water panel. 


How to Videos


Changing The Water Panel
Annual Maintenance
Aprilaire 500 Bypass Humidifier Overview
Aprilaire 500 Bypass Humidifier Water Panel Change
Aprilaire 500 Bypass Humidifier Maintenance


If you have any questions regarding this product, please use the HVAC.com Contractor Directory to connect with a trusted contractor in your area.

  • Brand: Aprilaire
  • Genuine OEM Part: Yes
  • Type: Bypass Humidifier
  • Control Type: Manual Non-Digital
  • Coverage: Up to 3,000 sq. ft.
  • Water Panel: Aprilaire #10
  • Evaporative Rate: .5 Gallons Per Hour
  • Bypass Diameter: 6"
  • Electrical: 24V
  • Product Measurements: 15.62" W x 13" H x 10.25" D
  • Plenum Opening: 9.5" W x 9.5" H
  • Drain Connection: .5" (I.D.)
  • Contains: 24 VAC Transformer, Manual Non-Digital Humidistat, Remote Temperature Sensor, Saddle Valve, 1 Aprilare #10 Water Panel
  • This product comes with a 5 year limited manufacturer's warranty from the date of installation.
    Reviews Write a Review
    • Jbird

      Installed easy, doesn't come with everything needed to install. Plan on going to the hardware store for $60 in extra supplies.. If I could do it all over I would of bought the better name brand with a install kit for $200.

    • gmteach00

      I installed this unit a few weeks ago and I noticed a different on my hygrometers within two hours of operation. My humidity was in the low 20's now its near the mid 30s.

    • Ron

      Great site. Referred there by my father-in-law!!

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    Aprilaire 500M - Bypass Humidifier 12 GPD with Manual Humidistat