Turn Off Power and Locate Your Filter

Before you touch anything inside your Aprilaire humidifier, switch it off at the power outlet or flip the breaker. Wait a few minutes for any residual moisture to settle. The filter sits inside the tank or behind a panel on the front or side of the unit, depending on your model number.

Open the access panel or remove the tank cover — most Aprilaire models use a straightforward latch or two clips that release by hand. Look for a rectangular or cylindrical filter made of pleated paper or foam. It will be white, tan, or gray and may look dusty or discolored if it needs changing. Write down your model number (usually on a sticker on the back or bottom) so you can order the exact replacement.

Key Takeaways

  • Always turn off and unplug the humidifier before opening it or touching the filter.
  • The filter is usually behind a front panel or inside the tank; your model number tells you which type you have.
  • Aprilaire filters typically last three to six months depending on water hardness and how often you run the unit.
  • Replacement filters cost between $15 and $40 and are sold online, at hardware stores, and through HVAC suppliers.
  • A clogged filter reduces moisture output and can cause mineral buildup inside the tank.

Remove the Old Filter Carefully

Grip the filter by its frame or edges, not the pleated material itself — squeezing the pleats can tear them and release trapped dust. Pull straight out toward you. If it is stuck, wiggle it gently side to side rather than forcing it; dried mineral deposits sometimes glue the filter to the housing.

Once the filter is out, look at the slot or bracket where it sat. Wipe away any white or tan mineral dust with a dry cloth or soft brush. Do not use water yet — you want to clear loose debris first. If mineral buildup is thick and hard, dampen the cloth slightly, but do not soak the housing or let water drip into the motor area.

Clean the Tank and Housing

While the filter is out, this is the best time to rinse the water tank. Empty any remaining water and rinse the inside with clean tap water. If you see white, chalky mineral deposits, fill the tank halfway with equal parts white vinegar and water, let it sit for 30 minutes, then scrub gently with a soft brush and rinse thoroughly.

Wipe the filter housing and the area around the motor with a dry cloth. Do not spray water directly into the motor or electrical connections. If mineral scale is heavy inside the tank, you may want to soak it longer or use a commercial humidifier descaling solution — follow the product instructions. Rinse everything well and let it air-dry for at least 15 minutes before installing the new filter.

Install the New Filter and Reassemble

Check the packaging or your manual to confirm you have the correct filter model for your unit. Aprilaire makes different filters for different humidifier sizes and types, so the wrong one will not fit or will not seal properly. Slide the new filter into the slot, pushing it straight in until it seats fully against the frame or bracket. You should feel a slight resistance as it settles into place.

Close the access panel or replace the tank cover and find any latches or clips. Make sure everything is tight so no air leaks around the filter edges — a loose filter lets unfiltered air bypass it. Plug the humidifier back in and turn it on. You should hear the fan start and feel moisture output within a minute or two.

Know When to Replace Your Filter

Aprilaire filters typically last three to six months of regular use, but that depends on your water hardness and how often you run the unit. If you live in a hard-water area, mineral buildup will clog the filter faster. Check it every month by opening the access panel and looking at the pleats — if they are visibly gray or brown with dust and mineral deposits, it is time to change it.

A clogged filter reduces the amount of moisture the humidifier can output and forces the motor to work harder, which shortens its lifespan. Some Aprilaire models have a filter indicator light that turns on when replacement is due; check your manual to see if yours has one. If you notice the humidifier is running but producing less moisture than usual, a dirty filter is often the cause.

Where to Buy Replacement Filters

Aprilaire filters are widely available online through Amazon, Walmart, and specialty HVAC retailers. You can also find them at most hardware stores in the heating and cooling section, though selection may be limited. HVAC contractors and local furnace dealers usually stock them and can order any model within a day or two.

Prices range from $15 to $40 depending on the model and where you buy. Buying a two-pack or three-pack often costs less per filter than buying one at a time. Keep your model number handy when shopping — typing it into the search bar will show you compatible filters and prevent ordering the wrong size.

Common Mistakes to Avoid

Do not try to clean and reuse an old filter by rinsing or vacuuming it. Pleated filters trap minerals and dust deep in the material, and water alone will not remove them. Once a filter is clogged, it stays clogged. Washing it can also damage the pleats and create gaps that let unfiltered air through.

Do not install the filter backward. Most filters have an arrow printed on the frame showing the direction of airflow — make sure the arrow points toward the motor or fan, not away from it. Installing it backward will reduce output and can damage the filter. If your filter has no arrow, check the manual or the packaging to confirm the correct direction.

Do not leave the humidifier running without a filter. The motor will pull unfiltered air and minerals directly into the tank and fan, causing buildup and reducing performance. Always install a new filter before turning the unit back on.

Frequently Asked Questions

How do I know what filter model my Aprilaire humidifier needs?

Find your humidifier's model number on a sticker on the back or bottom of the unit. Write it down and search for it online or call an HVAC supplier — they will tell you the correct filter. Do not guess; using the wrong size will not fit or will not seal properly.

Can I wash the filter instead of replacing it?

No. Pleated filters trap minerals and dust deep inside the material, and water alone cannot remove them. Washing can also tear the pleats and create gaps. Once a filter is clogged, replace it with a new one.

What if the filter is stuck and will not come out?

Turn off the humidifier and let it sit for 15 minutes. Mineral deposits sometimes dry and harden around the filter edges. Wiggle it gently side to side rather than pulling straight out. If it is still stuck, dampen a cloth and wipe around the edges to soften the deposits, then try again.

How often should I change the filter?

Most Aprilaire filters last three to six months depending on water hardness and use. Check it monthly by opening the access panel — if the pleats look gray or brown with dust and mineral buildup, it is time to replace it. Hard water clogs filters faster than soft water.

Why is my humidifier running but producing less moisture?

A clogged filter is the most common cause. Mineral deposits and dust block airflow and reduce output. Open the access panel and look at the filter — if it looks dirty or discolored, replace it. If the filter is new and output is still low, the tank may need descaling with vinegar and water.