Introduction to Humidifier Filters

Introduction to Humidifier Filters

What is a humidifier filter?

Water PadA humidifier filter is made to absorb water. There are three different types of filters. Most filters are either paper, metal or clay-coated. These filters absorb water and remove mineral deposits. Humidifier filters are typically coated with an antimicrobial coating designed to keep microbes from growing on the damp filter. Humidifier filters are also referred to as water panels, pads or evaporators.

How does the filter work?

The humidifier filter works by absorbing water. Hot, dry air from the furnace or fan coil pass through the filter and absorbs the water. The moist air is then distributed through the home via the forced-air duct system.

Why do you need a humidifier filter?

You may need a humidifier for a couple of reasons. Dry skin and sinuses are some of the more common reasons why people decide to get a humidifier. When your home is too dry it can cause a variety of health problems. You may also notice your wooden furniture is starting to crack and appears brittle.

The purpose of the humidifier filter is to absorb water. If you don’t have a filter in your humidifier, then it’s not going to work properly.

Do you need to change your humidifier filter?

You definitely need to replace your humidifier filter at least once every heating season. Over time they can become clogged and don’t work properly. Dust and air particles become trapped in the filter along with any minerals you may have in your water.

When your filter is dirty your humidifier unit works harder and less efficiently. In fact, a clogged filter could potentially be recycling dirty air back into your home since proper filtration is unable to occur.

How long will your humidifier filter last?

Whole house humidifier filters should be changed at least once every heating season. This basically means you should change your filter at least once a year. Most filters are labeled as lasting for six months, but filter life expectancy can range from 3 months to 12 months depending on the brand and material.

*Areas with hard water may require two filter changes per heating season to ensure peak performance.  This is due to the extra minerals found in hard water.

What should your humidifier filter look like?

Close Up Humidifier FilterHumidifier filters don’t look much different before and after using them. There is no certain color a humidifier filter should be since they’re all made of different materials. Humidifier panels range from white to different shades of brown and grey.

Your replacement filter may appear used due to the color, but it definitely is not. Some humidifier panels have darker coloring, which makes it appear as though it has already been used. Don’t worry though because we’d never resell any used merchandise.

Even though it’s sometimes hard to know when to replace your humidifier filter, as long as you make sure to change it at least once per year you should be just fine. Bottom line, you shouldn’t necessarily change your filter based only upon its appearance.

Types of Whole House Humidifiers

Whole house humidifiers are located within your Heating, Ventilating and Cooling system. They’re usually installed in the ductwork connected to your furnace. There are a few different options for whole house humidifiers. So, we’ve taken the liberty of identifying the most common types below.


Bypass whole house humidifiers use a water pad, or filter, to collect water. Your HVAC moves air through the pad, which then is absorbed into the air. Your furnace carries this moist air through your homes air ducts and circulates it throughout your home to increase humidity. Any unused water is usually drained from the humidifier via a drain line. Always make sure to replace the water pad according to the manufacturer’s directions.


This type of whole house humidifier has a rotating drum shaped frame. The water pad is rotated by the frame and passes through a pan of water. As the pad rotates it absorbs water. Warm air from the furnace passes through the pad and picks up moisture that’s distributed throughout the home. These require a little more maintenance because you have to replace the pad regularly and clean out the water pan to avoid any health risks. These humidifiers are usually the least expensive whole house option.

Steam Humidifier

Whole house steam humidifiers use a built-in heater to boil the water inside the humidifier until steam is produced. This steam is then directed into the duct system. These types of humidifiers don’t need the furnace to be on to function. If you have children, then this type of humidifier may be somewhat dangerous since its surface can get somewhat hot. This normally isn’t a problem though because whole house humidifiers aren’t generally located where children would have access to them.

Humidifier Operation

Is your humidifier working correctly?

Here are some of the things you should check if you’re worried your humidifier isn’t working properly:

  • Make sure your humidifier is turned on and set to the correct humidity level.
  • Is your furnace turned on? Most whole house humidifiers only work when your furnace fan is in use.

How to Turn Off Your Humidifier at the End of the Season

Be sure to turn off your humidifier at the end of the winter months. Many people forget to switch it off before summer starts, which is a major problem since your air conditioner won’t run correctly if the humidifier is still on.

To turn off your humidifier:

  1. HumidistatTurn the humidistat to the off position. If there is no off position, then make sure it’s at the lowest humidity level.
  2. Close the bypass duct damper if your humidifier has one.
  3. Turn off the water supply to the humidifier.
  4. Clean and replace the humidifier filter.

*Contact a professional if you don’t feel comfortable performing any of these steps.

Ideal Humidity Level

There is no ideal indoor humidity temperature; rather there is a range of acceptable levels. You should keep your home’s humidity between 20 percent and 60 percent year round. The exact percentage should depend on what level your home’s residents feel most comfortable. In the winter, make sure to set your humidity above the 20 percent mark and preferably above 30 percent. In the summer, don’t let the indoor humidity go above 60 percent.

Read our article on How to Use Your Humidifier for more information on humidifier operation.

What to do if your humidifier is leaking?

If there is excess water in your humidifier, then there’s probably something wrong with your humidifier. You may even have a leak, which can be quite costly if you don’t catch it in enough time.

The problem may be caused by one of the following issues:

  • Water backing up into the drain line – Make sure the drain line is free of kinks. Run water through the drain to see if it’s clogged. Replace your drain line every year to prevent this problem from occuring.
  • Clogged Water Pad or Scale Control Insert – Check the water pad for dirt or debris. Clean the scale control insert and install a new pad to fix this problem.
  • Solenoid Valve – Make sure the valve is pointing the correct direction. If a piece of dirt or debris lodges between the valve plunger and seat on the solenoid, then the valve is unable to completely close. This causes the solenoid valve to leak. Before you go any further, make sure you turn off the water supply and disconnect electrical power to your furnace.
  • Water Pressure – Check your pressure level, it should be above 125 pounds per square inch.

Read our article Leaking Humidifiers for more information.

Where to buy replacement parts and filters?

Find replacement whole house humidifier filter here.

Find replacement portable humidifier filters and wicks here.

Shop humidifier parts here.

Find a humidifier here.

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