This is what happens if you don't change furnace air filters

17 Replies

Yesterday I got a call from a tenant telling me that his furnace would make an unusual noise when he turned on the AC the first time (yes, end of June - that's one of the perks of living in Wisconsin). I asked him to turn off the system and I would check it out after work. When he called me he was surprised that I could not hear the noise over the cell phone, which really got me to worry a little. So I got there turned on the unit and indeed it sounded like when you throw tennis shoes in a dryer and the whole system was shaking. Clearly the fan was completley out of balance, so I checked the filter and to my surprise -  there was no filter! What I found in the fan was this:

It looks like the remains of an old dirty filter! Somehow it must have collapsed and got sucked into the fan. Not quite sure how a filter goes from dirty to shredded?? Makes me wonder if anyone has seen this before or if there was something else going on? I suspect the the heat exchanger is full of dirt and will have the unit cleaned  serviced. My tenant was surprised about what I found - and the fact that filters need to be changed. I learned another lesson here - from now on I will replace filters no matter what my tenants tell me. Looks like this is what most of you guys do as well?

Yes, you need have an organized filter changing schedule.  Hell will freeze over before any of my tenants buy and change their filter.

hi marcus. yes, filters need to be changed often. in fact, i recommend at least once a month, depending on the location of your furnace and cold air return system. that being said, here is my experience and expertise. ( i just competed getting my certification in furnace repair). the purpose of the cold air and fan are to circulate the hot air to the area where heat is needed. but the purpose is also to cool the heat exchanger in the furnace as well. the heat exchanger is a sealed system of pipes that the heat created by the burners heats up. the air from the fan/ cold air return blows passed the heat exchanger to circulate the heat to other areas and to cool the heat exchanger. if the filter is clogged, no air gets past the heat exchanger and consequently, the heat exchanger will overheat and get damaged. i have personally seem the heat exchanger with massive holes in it due entirely to a clogged filter. it is highly unlikely that your heat exchanger inside is full of dirt, but the fan and area around the heat exchanger could be filthy

Filters are the cheapest maintenance item in a house. You can get them in bulk for around $3.00 each from a filter company near Butler for the 1" wide ones. You don't need the most expensive ones from the hardware store. I usually get the mid grade ones and have not had an issue with them for over 12 years.

I try to replace filters at 3 month intervals. 

This also get you or an employee into the property for an inspection and battery test on the smoke and CO detectors.

Looks like the carcass of a BAT!

We check or change the furnace filters every three months. If the tenant has fur bearing pets, monthly. Going inside the unit every three months helps us know if the tenant is abiding by the terms of the rental agreement or not. It is also easier to keep up on other routine maintenance at the same time and gives us an opportunity to nurture the landlord-tenant relationship.

Thanks for sharing the photo. Never saw anything like that!

I got a couple of good chuckles over this.  I feel your pain.  Just when I think I'm a brilliant real estate investor I am reminded that I'm really in the furnace filter business.  I put it in the lease the filters must be changed as needed using only "pleated" filters, otherwise they will use the $ .88 ones that are worthless.  I remind the tenant that if  I experience costs that could have been prevented by changing the furnace filters I will recoup those costs from them. But, that has never actually happened.

I also thought it was a Bat.

Bats are known minor issue on Milwaukee Northwest and East side.

I typically suggest changing furnace filters at least 2 times a year.

( during September and February )

My personal feelings the best options for purchasing furnace filters 

would be Home depot, Lowes, and Wal-mart.

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I send letters out several times a year telling tenants that we are coming out to inspect the property and give them some ideas of violations that may occur like "replacing furnace filter, batteries in smoke detectors, yard and trash.  We don't actually do this for every property each quarter, but randomly pick properties each quarter. We also remind tenants to change their filter and it will reduce their utility bills.  Lowe's has a free account "MY LOWE'S"  to help you track products by property (paint color, filters, etc..) Any product you purchase they scan it and you can access it online.

Funny, Thanks for sharing!

We always change the filters when we do a scheduled property inspection. We manage over 1300 properties and I can think of maybe 3 tenants who change their filters.

Truth is, people who rent never learn how to take care of a home.

Homeowners learn how out of necessity.

Originally posted by @Glenn McCrorey :

I got a couple of good chuckles over this.  I feel your pain.  Just when I think I'm a brilliant real estate investor I am reminded that I'm really in the furnace filter business. 

Glenn, your comment about self perception made me laugh! You are absolutely right and I can't tell you how many I went from feeling brilliant for closing an unbelievable deal to feeling stupid in a matter of minutes. I think this is what makes REI so interesting. And this is also why I love the BP community: because you guys understand this.

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I add this to the calendar on my phone and personally replace the filters. I just don't trust the tenants to do it and it is too large of an expense should something go wrong with the furnace because of such a cheap and easy maintenance routine.

I usually keep a couple filters around the furnace in the rental property so I don't have to remember the size each time I go there and I don't have to make a stop at Home Depot just for that purpose.

@Tyson Luthy  @Jeff Semrow@Mark Elliott and everyone else -  thanks for your comments, you make a strong case here! I change filters in my duplex, but for some reason I thought it would be different in my SFs. I guess I will be buying some filters..

Jeff, would you PM me the contact of the business in Butler?

@Marcia Maynard now that you say it... but it's positively a pile of dirty filter pieces and not a bat!

@Marcus A. Thanks Marcus. I feel the same way about my fellow REI folks on BP. None of my friends are involved in REI which is why I like BP so much.

I tell all potential tenants that every 3 months I will change filters explaining that it saves my equipment and saves them money on heating and cooling I also look under sinks for leaks. Last month I found a kitchen faucet leaking under the sink.

I have found that 3 months is sufficient since I have gotten rid of most of my carpet. 

Check out We have a tenant program that helps insure your tenants are changing out their filters. If you would like more information feel free to message me!

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