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What filter does a GeneralAire 4400 take?

It takes the GeneralAire GA35 Water Panel — OEM part number GA35.

GeneralAire 4400, whole-house humidifier, whole house.

Lowest verified price: $15.52 — aftermarket, 1 panel, BestAir A35 aftermarket at SupplyHouse. Free shipping on orders over $99 at SupplyHouse; a fee applies below that. Checked 2026-11-11.
Buy the GA35 on Amazon — GA35Amazon search for the exact part number (no single listing is endorsed). Amazon price is shown on Amazon; we do not quote it here.

The part, in brief

PartGeneralAire GA35 Water Panel
Replacement intervalReplace annually.
EquivalentsAprilAire 35, Filters Fast A35PR

Verified prices

OptionPriceStore & shipping
Genuine (OEM)
1 panel, genuine GeneralAire GA35
$19.38SupplyHouse
Free shipping on orders over $99 at SupplyHouse; a fee applies below that · Checked 2026-11-11 · source
Aftermarket
1 panel, BestAir A35 aftermarket
$15.52SupplyHouse
Free shipping on orders over $99 at SupplyHouse; a fee applies below that · Checked 2026-11-11 · source
Genuine (OEM)
1 panel, genuine AprilAire 35 (the equivalent panel for 4200/4400)
$34.95FiltersFast
Free economy shipping on orders $99+ (lower 48); a fee applies below that · Checked 2026-11-11 · source

Full record with every price, source and date: GeneralAire GA35 Water Panel page.

Finding the model number on a GeneralAire

Whole-house models: the model number is on the cover of the unit mounted on the ductwork. The vapor pad number (990-13, GA19) is in the manual and on the old pad's packaging.