Things You Need to Know About Changing Furnace Filters

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Changing furnace filters is a relatively easy task that many homeowners decide to accomplish for themselves. There’s no question that changing your furnace filter on the proper schedule is important. It helps improve your indoor air quality and your HVAC system won’t need to work as hard.

If you do decide to change your furnace filter there are a few things you should know to make the task easier.

There are Different Filter Sizes

You cannot buy just any furnace filter and expect it to fit. You will need a furnace of a specific length, width, and height in order to replace your current filter. The simplest way to do this is to look at the current filter you have and match the new ones to it. If you’re not satisfied with the width of your filter, you can sometimes get your HVAC professionals to adjust your ducts to allow for a thicker filter.

There are Different Filter Qualities

Furnace air filters are key to keeping little particles out of your furnace. Otherwise, they could build up inside and reduce its efficiency, eventually damaging it. High-quality filters will pick up smaller particles and will thereby provide better protection for your furnace. They may also have an impact on your overall air quality.

Air filter quality is measured in MERVs, or minimum efficiency reporting value. The higher MERV, the smaller and larger percentage of particles that the filter can pick up. However, not all MERV levels are compatible with furnaces.

If you have questions about your furnace filters, give our team at Guest Plumbing and HVAC a call today. We’re here to help!

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How Often to Change 1/2/3/4-inch Furnace Filter

You should change your furnace filters based on how thick they are. A thicker filter has more room for contaminants and can be left in the furnace for longer. Here’s how often you should change each filter:


  • 1 to 2-inch filters: Replace every 1 to 3 months.
  • 3 to 4-inch filters: Replace every 6 to 9 months.
  • 4 to 6-inch filters: Replace every 9 to 12 months.

How Often You Should Change Your Furnace Filter if You Have Pets

You may also need to change your furnace filter more often if you have pets. That’s because pet hair and pet dander fill up filters quickly. If they form a mat, they will restrict airflow through the furnace which can cause great damage to the furnace. Ask a professional how often you should be changing your own filters.

When to Change Your Furnace Filter

If an HVAC professional were to change your furnace filter, they would complete the furnace filter change during their maintenance appointment. You should change the filter before you start up the furnace for the year, and then on the schedule listed above until the end of the season. Don’t forget to change your filter when the AC is on too!

It is recommended by HVAC professionals that you change your filter at least once before you start up your furnace for the year. After that, you should change it based on the guidelines listed above for each filter size.

Have you changed your furnace filter lately? If it’s been a while, it may be time to change it. To book an appointment or to learn more about furnaces and maintenance, contact our team at Guest Plumbing & HVAC today!


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