Aprilaire Humidifier Pads 10 / 12 / 35 / 45 (and the 600 EZ Kit): Which Fits Which Humidifier?
Quick answer
Match the pad to your humidifier model. Aprilaire's 35 fits the 600 and 700 families, the 45 fits the 400 family, the 10 fits the 500 family, and the 12 fits older 440/445-style units. [S1] [S2] [S3] [S4] [S5]
- The 35 and 45 share a nominal 13 × 10 × 2 in size, but Aprilaire lists different humidifier models for each. Do not swap them. [S1] [S2] [S5]
- Aprilaire says to replace Water Panel 10, 12 and 35 once per heating season, and Water Panel 45 twice per heating season. [S5]
- For Models 600, 600A and 600M, Aprilaire also sells a 35 Water Panel EZ Kit that includes the scale-control insert, distribution tray and a 35 pad. [S6]
Which Water Panel fits which humidifier
| Water Panel | Nominal size (H × W × D) | Actual size (H × W × D) | Humidifier models Aprilaire lists | Replace | Source |
|---|---|---|---|---|---|
| 10 | 10 × 10 × 2 in | 9.75 × 9.5 × 1.75 in | 110, 220, 500, 500A, 500M, 500MKZ, 500KZ, 550, 550A, 558 | Once per heating season | [S3] [S5] |
| 12 | 15 × 12 × 2 in | 14.75 × 11.5 × 1.75 in | 112, 136, 224, 440, 445, 445A, 448, Chippewa 224, Chippewa 225 | Once per heating season | [S4] [S5] |
| 35 | 13 × 10 × 2 in | 13 × 10 × 1.75 in | 300, 350, 360, 560, 560A, 568, 600, 600A, 600M, 600MKZ, 600KZ, 700, 700A, 700M, 700KZ, 700MKZ, 760, 760A, 768 | Once per heating season | [S1] [S5] |
| 45 | 13 × 10 × 2 in | 12.875 × 9.875 × 1.75 in | 400, 400A, 400M, 400KZ, 400MKZ | Twice per heating season | [S2] [S5] |
Aprilaire's Home Depot page lists a shorter model set for each pad; the shop pages above add the KZ/MKZ variants. Home Depot also lists Model 225 with Water Panel 12. [S5]
600-series EZ Kit
| Kit | Includes | Fits | Source |
|---|---|---|---|
| 35 Water Panel EZ Kit for 600-series | 4330 scale-control insert, 4331 distribution tray, and a 35 Water Panel | 600, 600A, 600M | [S6] |
Read the humidifier model, not just the pad size
Water Panel 35 and Water Panel 45 are both sold around 13 × 10 × 2 in, but Aprilaire assigns them to different humidifiers. [S1] [S2] [S5] Buying by size alone is how people put a 45 into a 600 (or the reverse). Check the model number on the humidifier cabinet or the owner's manual.
Related Aprilaire guides
Looking for the whole-house air cleaner filters instead of humidifier pads? See Aprilaire 201 vs 213 vs 413. For furnace filter sizes in general, see the furnace filter size chart.
Where to buy
We don't list prices because they change daily. Check the current price at the seller.
- AprilAire: Water Panel 35 Official: Manufacturer store. Check current price.
- AprilAire: Water Panel 45 Official: Manufacturer store. Check current price.
- AprilAire: Water Panel 10 Official: Manufacturer store. Check current price.
- AprilAire: Water Panel 12 Official: Manufacturer store. Check current price.
- AprilAire: 35 Water Panel EZ Kit (600-series) Official: Manufacturer store. Pad plus tray and scale-control insert. Check current price.
FAQ
Is Water Panel 35 the same as Water Panel 45?
No. They share a nominal 13 × 10 × 2 in size, but Aprilaire lists different humidifier models and different change intervals. [S1] [S2] [S5]
Which pad does my Aprilaire 600 take?
Aprilaire lists Water Panel 35 for Models 600, 600A and 600M. [S1] [S5] The 600-series EZ Kit packages that pad with the tray and scale-control insert. [S6]
Which pad does my Aprilaire 400 take?
Aprilaire lists Water Panel 45 for Models 400, 400A and 400M (plus 400KZ / 400MKZ on the shop page). [S2] [S5]
Which pad does my Aprilaire 500 take?
Aprilaire lists Water Panel 10 for Models 500, 500A, 500M and related 550/558 units. [S3] [S5]
How often should I change the pad?
Aprilaire says once per heating season for Water Panels 10, 12 and 35, and twice per heating season for Water Panel 45. [S5]
Is this the same as an Aprilaire 213 air filter?
No. Water Panels are humidifier evaporative pads. The 201 / 213 / 413 family is for whole-house air cleaners. See Aprilaire 201 vs 213 vs 413.
What we could not verify
- Exact change steps and photos for every humidifier model. Aprilaire's blog points to model-group videos; we didn't re-verify each video transcript.
- Whether every Chippewa-branded unit on the Water Panel 12 list is still supported. The shop page names Chippewa 224 and 225. [S4]
Sources
- [S1] AprilAire 35 Replacement Water Panel Humidifier Filter, AprilAire. Accessed 2026-10-28. Used for: Compatible humidifier models, nominal and actual size for Water Panel 35.
- [S2] AprilAire 45 Replacement Water Panel Humidifier Filter, AprilAire. Accessed 2026-10-28. Used for: Compatible humidifier models, nominal and actual size for Water Panel 45.
- [S3] AprilAire 10 Replacement Water Panel Humidifier Filter, AprilAire. Accessed 2026-10-28. Used for: Compatible humidifier models, nominal and actual size for Water Panel 10.
- [S4] AprilAire 12 Replacement Water Panel Humidifier Filter, AprilAire. Accessed 2026-10-28. Used for: Compatible humidifier models, nominal and actual size for Water Panel 12.
- [S5] AprilAire and Home Depot, AprilAire. Accessed 2026-10-28. Used for: Filter sizes, humidifier model lists, replace-once vs twice per heating season.
- [S6] AprilAire Humidifier Filter / Water Panel Assembly Replacement Kit 600, AprilAire. Accessed 2026-10-28. Used for: EZ Kit contents (4330, 4331, 35 pad) and fit for 600, 600A, 600M.
Last checked 2026-10-28. Spot an error? Tell us and we'll recheck it against the source.