How To Clean a Reusable Furnace Filter

February 21, 2024

Furnace filters come in different sizes, thicknesses, and designs but the most basic distinction for homeowners is whether they are disposable or reusable.

Disposable filters must usually be replaced every few months but reusable furnace filters can be cleaned repeatedly. This makes a little more work but saves money and is generally better for the environment.

But how do you even know if your filter is reusable and, if it is washable, how do you clean it so that it does its job properly in your home heating system?

Here’s everything you need to know about cleaning a reusable furnace filter, including a step-by-step guide to removing and washing it…

Disposable vs reusable furnace filters

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Disposable furnace filters made of pleated paper or fiberglass have been available since the 1940s and remain the most popular type of furnace filter in Alberta.

Modern designs are usually soft to the touch and cannot be reused but they are considered convenient and effective in trapping dust and debris. At the end of their short lives, they’re simply binned.

In the 1990s, as the drive towards more sustainability started in earnest, reusable and washable filters started to appear more. These filters have generated more interest in Canada over the last couple of decades. They usually cost about five or six times more than disposable filters but they reduce waste and provide a cost-effective, long-term solution for filtering air in a furnace.

Reusable furnace filters are typically made of electrostatically charged woven polypropylene, which attracts impurities to its surface. If well-maintained, these filters can last 5-10 years—compared with most disposable filters that last only a few months.

How do you know if your furnace filter is reusable?

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Surprisingly, perhaps, it’s not always immediately obvious whether your furnace filter is disposable or washable. Nobody keeps the packaging from air filters after all.

That said, it should indicate somewhere on the filter itself inside your furnace whether it can be cleaned and reused. You can check with the manufacturer or your furnace outlet if in any doubt.

If you’re still not sure, ditch the old, dirty filter in your furnace and replace it with one that you know is reusable.

Why is cleaning a furnace filter important?

If you have a washable furnace filter and never clean it or change it, sooner or later your heating system will seize up. And we all know what that feels like in midwinter in Alberta.

Before then, it’s likely to lead to countless issues with inadequate heating, poor air quality, and all-round implications for your family’s comfort levels.

The filter is responsible for circulating clean air through the furnace and out into your home. It gathers dust, dirt, and other airborne contaminants just before the air is pulled into the furnace system.

Most reusable filters are highly effective at removing particles of size 0.5 microns or larger from the air (visible to the naked eye) as well as smaller, less-visible contaminants.

For a furnace to heat your home properly, air must circulate freely through the heating system. A clogged or dirty air filter will prevent this and cause many common furnace problems leading to poor heating performance. Dirty filters cause the unit to work harder than it should, leading to extra wear and tear and a shorter furnace lifespan. Severely clogged filters can even shut down the entire heating system and require emergency furnace repairs.

Another reason why it’s important to wash reusable furnace filters is that dirty filters can affect indoor air quality, which can be particularly serious for allergy or asthma sufferers.

Even though your furnace may sit quietly in the basement, attic or closet and do its job, essential maintenance tasks like cleaning the filter should not be forgotten or big problems will result.

Furnaces are a major investment for most Calgary homeowners. Protecting your investment with regular cleaning and maintenance is simply common sense.

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How to clean a reusable furnace filter

How can you remove a reusable furnace filter, wash the dust and debris off it, and place it back into your HVAC system so that it works as well as new?

Follow these steps:

1. Shut off the power to the furnace. This applies whenever you open up the access panel of your furnace.
2. Remove the reusable air filter from the unit. Open the access panel; the filter is likely located in a slot in the bottom section of the furnace, next to the air handler, which contains the blower motor. The idea is that air entering the heating system is filtered before being circulated by the blower fan.
3. Rinse the filter with plain, warm, distilled water. Use tap water if that’s all you have but distilled water is purer and less “hard” than Calgary tap water so it is less likely to cause residue. You might want to rinse the filter in a tub or sink.

Use gentle household detergent to wash the filter. Dish soap or ordinary hand soap is suitable as effectively removes dirt and grime without damaging the filter.

Use a soft brush or low-pressure vacuum hose to gently clean the filter. This will provide a deeper clean and remove any caked-on dirt—but be careful not to damage the filter.
Re-rinse the filter using distilled or tap water. Make sure that all the soap and dirt are gone.
Gently shake out excess water from the holes in the frame and dry it thoroughly. Make sure the filter is completely dry before replacing it in the furnace and closing the access panel.

Turn on the furnace to start using it again.

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Always check and confirm instructions for cleaning and maintaining your reusable filter with your filter/furnace manufacturer so that you don’t compromise the respective warranties.

Which way should the furnace filter go?

If you’re unsure which way to re-insert the furnace filter after cleaning it, there should be an arrow indicating the direction of the airflow.

The filter should be installed with the arrow pointing toward the direction of the airflow of the furnace. If you’re still unsure, check out our article What Direction Does the Furnace Filter Go?

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Which side of a furnace filter should be dirty?

New air entering the furnace should flow through the front of the filter and any dust or debris should be collected in the mesh.

Can I use bleach to clean a washable furnace filter?

It’s best to use gentle household detergents to clean furnace filters. Bleach does not come into that category and is best avoided.

Since most of the dirt and grime trapped in an air filter is easily removed and doesn’t pose a major health threat, bleach should not be necessary as it could damage the delicate materials used in filters and shorten their lifespan.

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What happens if you wash a disposable filter?

Disposable filters are designed to be just that—disposed of after one use. If you wash and reinsert a disposable filter in your furnace, it will likely get messy, encourage mold growth, and damage the efficiency of your heating system.

How often should you clean your furnace filter?

Furnace filters need cleaning or replacing when they’re dirty. This simple fact applies everywhere but different homes use different filters and have different indoor air conditions. This means that the frequency with which you should clean reusable filters varies.

A good guideline is to clean your filter every one to three months. If you have pets, a lot of dust, and many occupants in your household, clean the filter every month.

If the indoor conditions are relatively free of dirt and pet dander (or you run an air purifier), a clean every three months may be sufficient.

You should also clean your reusable furnace filter after a period of disuse for your heating system or if the filter has been in storage for a while. If you need to store your filter, choose a dry and dust-free location.

The brand and thickness of your reusable furnace filter will also affect its cleaning requirements. The thicker the filter, the higher its capacity to hold dust from the air, which may mean less frequent cleaning is required than for thinner designs.

If you’re replacing a reusable filter, purchase one that fits properly into your furnace, i.e., of the right thickness. Filter thicknesses range from one inch to five inches.

What are the signs that my furnace filter needs cleaning?

Dirt builds up gradually inside an HVAC system and starts to clog the filter. This “invisible” and silent process can be difficult to detect without frequent manual inspections of your furnace.

An annual furnace maintenance or tune-up is not sufficient to properly check filter performance so it’s best to schedule reminders every couple of months to check your furnace filter.

Hold the filter up to the light. If it looks clogged or you can’t see the light through it relatively clearly, the filter needs a clean.

A clogged filter may also lead to other signs that something is wrong with your furnace. Here are some tell-tale signs that you should be on the lookout for with your heating system:

Unexplained increases in heating bills and energy costs
Poor heating performance (rooms not heating up adequately)
The furnace is blowing cold air
Poor air quality inside the house
Unexplained shutdowns of the heating system
Increase in allergies or breathing issues for household occupants

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What happens if you don’t clean your furnace filter?

If you don’t clean a reusable furnace filter, issues can crop up with your heating system at any time of the year.

A cold home is no fun for anyone. If filters are clogged, your family’s comfort is at stake. The air quality in the home may also be poor and cause health issues.

The lifespan of the furnace may also be reduced by excessive wear and tear, repair bills for damaged components may be high, and monthly energy usage higher than necessary from an overworked system—which can cause financial strife.

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Furnace tune-ups in Calgary

Cleaning your furnace filters regularly can enhance the performance, energy efficiency, and longevity of your HVAC system. It will also maintain the air quality and comfort levels in your home and reduce wastage.

We provide year-round furnace tune-ups for all types and brands of furnaces in Calgary. All of our furnace professionals are SAIT-certified and highly trained to get the job done efficiently.

Call us at 403-236-4366 or contact us online to book furnace maintenance.