Whole-house furnace humidifier replacement water panels and pads: AprilAire 10/35/45 water panels and EZKits, Honeywell HC22E1003/HC26E1004 pads, and OEM vs compatible multipacks, matched by humidifier model number and pad dimensions
Find the model number before you look at any panel
A bypass or flow-through whole-house humidifier mounts on the supply plenum or return plenum and passes water over an evaporator pad. Warm furnace air crosses the wet pad and carries moisture into the ducts. The pad is a wear part. Its shape is set by the humidifier housing and its water distribution tray, so the panel number has to follow the humidifier model, not the furnace.
The model number is on a data label, usually on the humidifier cover or inside the case once you remove the cover. AprilAire units are numbered in the hundreds (for example 400, 500, 600, 700). Honeywell Home units use an HE prefix (HE220, HE265, HE360). Photograph the label before you shop, because a panel that looks right in a thumbnail is often one size off.
If the label is gone or painted over, measure the old pad. Height, width and thickness in inches are the nominal size that parts sellers list. Treat the measurement as a cross-check, not a substitute for the model number, as the next sections explain.
AprilAire 10, 35 and 45: what each one fits
AprilAire sells its panels by number, and the number does not rise with humidifier capacity in any obvious way. These are the current fitment lists on AprilAire’s own shop pages:
- Water Panel 10: models 110, 220, 500, 500A, 500M, 550, 550A and 558.
- Water Panel 35: models 300, 350, 360, 560, and the 600 and 700 series.
- Water Panel 45: models 400, 400A and 400M.
- Water Panel 12 (adjacent part): listed for models 112, 224, 225, 440, 445, 445A and 448 on AprilAire’s storefront. It is a separate panel and not interchangeable with the three above.
The 35 and 45 are the pair most often confused. Sellers measure both at about 10 inches high by 13 inches wide, with thicknesses of roughly 1.75 and 1.5 inches. The footprint is nearly identical, but the panels are not interchangeable. The thickness, the frame fit against the water distribution tray, and the way water meters across the pad all differ. Buy by humidifier model, not by “it looks the same size.”
AprilAire also sells EZKit bundles, such as the 35 EZKit. Check the listing for exactly what is packed with the panel, because the contents differ from the bare panel multipack.
Honeywell HC22E1003 and HC26E1004 pads
Honeywell Home’s bypass humidifiers use pads with an AgION antimicrobial coating in the HC22E1003 and HC26E1004 versions. Resideo’s product overview pairs the HC22 family of pads with its small bypass humidifier and the HC26 family with its large bypass humidifier. Each size also comes in a standard-coating version.
Dealer listings match the HC22E1003 to the HE220 and HE225. They match the HC26E1004 to the HE265 and HE365, and some listings also name the HE360 and other large bypass units. Treat the listing as a starting point and confirm against the humidifier’s own data label. The HC26E1004 is listed at 10 x 13 x 1.5 inches, which is a close match to AprilAire’s panels. That similarity is the reason mix-ups happen, because the pad can seem to fit by hand and still sit wrong in the tray.
A pad that does not seat flush lets air bypass the wet surface and can leave gaps where water spills past the tray. Dealer sites carry most of the Honeywell range. The HC26E1004 is also listed on Amazon, but check whether the seller is the OEM channel or a third party before ordering.
Model-to-panel compatibility table
| Humidifier model | Replacement panel or pad | Type |
|---|---|---|
| AprilAire 110, 220, 500, 500A, 500M, 550, 550A, 558 | AprilAire 10 | Bypass, panel |
| AprilAire 300, 350, 360, 560, 600 series, 700 series | AprilAire 35 | Bypass, panel |
| AprilAire 400, 400A, 400M | AprilAire 45 | Bypass, panel |
| AprilAire 112, 224, 225, 440, 445, 445A, 448 | AprilAire 12 | Panel |
| Honeywell HE220, HE225 | HC22E1003 (AgION) | Bypass, pad |
| Honeywell HE265, HE365 (and listed large units such as HE360) | HC26E1004 (AgION) | Bypass, pad |
If your model is not in the table, do not guess from the nearest row. Look up the full model number, including any suffix such as A or M, on the manufacturer’s parts page. The suffix can mark a revision with a different tray or controls, though the panel number often stays the same. Check the manufacturer’s list rather than assuming. A humidifier with a drum, a fan-powered housing or an atomizing nozzle uses a different wear part from a flat panel, and none of the above will fit it.
OEM versus compatible multipacks
Compatible panels are sold as 2-packs and 3-packs, usually labeled “35” or “fits 35,” and many use aluminum mesh. A named third-party brand such as BestAir also sells a 35-equivalent. The appeal is cost per season. With a multipack you buy the replacement for several seasons at once.
The trade-offs are about fit and material, not brand loyalty. An OEM panel is made to the exact thickness and frame the tray expects. A compatible panel may differ by a fraction of an inch in thickness, in how rigid the frame is, or in the mesh coating that takes up the scale. A pad that is slightly too thick can bind in the tray. One that is slightly thin can let water run behind it instead of through it. Either problem shows up as a pad that dries out unevenly, or as water on the humidifier floor.
AprilAire and Honeywell both state in their literature that their products are designed for their own housings. A compatible panel is a reasonable choice when the listing gives the exact model numbers it fits and the dimensions are posted. It is a poor choice when the listing says only “universal” or copies a different panel number. If the humidifier is under warranty, check whether the manufacturer requires genuine parts before you substitute.
Hard water, scale and replacement timing
Water flowing across the pad evaporates and leaves its dissolved minerals behind. The result is scale on the mesh or media, which blocks the pores, reduces evaporation and eventually stiffens the pad. Hard water speeds this up considerably. A pad that feels stiff, looks crusted white or tan, or crumbles when pressed is past its useful life, however long it has been installed.
The usual practice is to replace the panel once per heating season, and sooner in hard-water homes. Do it before the start of the season so the first cold weeks do not run on a clogged pad. At the same time, look at the water distribution tray, the orifice or solenoid valve that meters water, and the drain line. A blocked orifice starves the pad. A blocked drain can overflow into the plenum.
If the pad is dry in one corner while the rest is wet, the problem is usually the tray or the orifice, not the pad. A fresh panel will not fix that. Clean the tray, clear the orifice, then fit the new pad. When the pad has dried out all season and the humidistat is satisfied, check the water supply (saddle valve or tee) and the humidistat setting before assuming the panel failed.
Installation mistakes that waste a good panel
Turn off the water supply and the humidifier power before touching the unit. Slide the old pad out of the tray, noting which way it faces, since some designs have a front and back. Rinse the frame and tray, and let them drain before inserting the new pad.
Common mistakes are fitting the panel backwards, leaving the protective wrap on, and forcing a near-fit panel into a tray built for another number. Another is replacing the pad without resetting the humidistat or the damper, which leaves the humidifier unable to pull airflow across the media. For bypass units, confirm the bypass damper is open when the humidifier runs, so air actually moves through the panel.
After fitting the panel, run the humidifier and look for even wetting across the face within a short time. Water that sheets down the pad evenly is what you want. Water that runs only down one side, or drips from the bottom edge of the frame, means the pad is not seated or the tray is blocked.
Related guides
- AC and mini split coil-cleaning supplies: mini split cleaning kits and wash bags, no-rinse and foaming evaporator/condenser coil cleaners, fin combs, and soft brushes (by unit type: wall-mounted mini split indoor head, outdoor condenser, window AC)
- AC and mini split condensate management: condensate pumps, drain-line clog prevention and overflow protection
- Best Air Purifiers for Allergies (2026)
- Best Ceiling Fans for Large Rooms (2026)
FAQ
Can I use an AprilAire 35 panel in a humidifier that takes a 45?
No. The two panels are close in size, about 10 by 13 inches, but their thickness and fit against the tray differ. AprilAire lists the 45 for models 400, 400A and 400M, and the 35 for the 300, 350, 360, 560, 600 and 700 series. Use the panel listed for your model number.
How often should I replace a whole-house humidifier water panel?
Most manufacturers recommend replacing it once a heating season, and sooner if you have hard water. Replace it when it feels stiff, looks crusted with scale, or no longer wets evenly. Fit the new one before the heating season starts.
Are compatible multipacks as good as OEM water panels?
They can be, when the listing names your exact humidifier model and gives dimensions that match. The risk is a pad that is slightly the wrong thickness or has a looser frame, which causes uneven wetting or water spilling past the tray. If you are unsure of the match, buy the OEM panel.
What is the difference between the Honeywell HC22E1003 and HC26E1004?
Both are AgION-coated pads for Honeywell bypass humidifiers. Dealer listings match the HC22E1003 to the HE220 and HE225, and the HC26E1004 to larger units such as the HE265 and HE365. Confirm your humidifier’s model number before ordering.