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When to change 25x16x5 furnace filter

  • Last Updated:
  • Aug 2nd, 2020 1:58 pm
Sr. Member
Jan 14, 2010
686 posts
228 upvotes
Central Ontario
I change CT MERV8 25x6x1 filters monthly. I left it go ~7 weeks by accident recently (run fan in continuous mode, esp with AC on) and it was filthy. $10 every 3 months is nothing to keep your furnace cleaner. Do 5" last so much longer?
Deal Fanatic
Jan 31, 2007
5028 posts
5145 upvotes
Richmond Hill
I change them approx every 6 months. When I switch from heat to AC, and AC to heat.

At the same time is turn on/off humidifier as well.
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Deal Expert
Aug 2, 2004
36357 posts
9621 upvotes
East Gwillimbury
cocodc wrote: Do 5" last so much longer?
The bigger the filter, the better

The pleats are not as close together as 1” filters thus giving you more surface area. The V shape on a 1” filter is a lot smaller and closer together allowing dust to easily accumulate. On a larger filter, the V angle is more obtuse.

This gives you more air flow.
Deal Addict
Apr 5, 2009
1056 posts
296 upvotes
I change my 4 or 5 inch wide filter everytime I enable or disable the humidifier... fall and spring... about 6 months
Deal Expert
User avatar
Oct 6, 2010
15508 posts
10156 upvotes
Toronto
There's a few threads on them. Pete gave the link above. You can cash and carry, example, I paid $45 for 12 16x25x1
250strong wrote: Where does everyone buy their filters? And how much do they cost?

16x25x4

What do you think of these?

https://www.amazon.ca/Filtrete-Replacem ... lp_pl_dp_1

Or furnace filters.ca?

https://www.amazon.ca/16x25x4-Furnace-F ... lp_pl_dp_9
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Deal Expert
User avatar
Dec 23, 2003
16805 posts
5389 upvotes
Toronto
Filters all come down to usage and environment. Our 16x25x5 gets inspected every 3 months. After that, we check it every month and gets changed when it starts looking dirty compared to the new one (after 5 to 6 months). Changing the filter is easier than having to clean the AC coil in the ductwork that has dirt built up due to a dirty filter.

I would suggest you get the cheapest 16x25x5 filter so it puts less stress on the motor.
Member
May 7, 2016
483 posts
417 upvotes
cheapshopper wrote: I change them approx every 6 months. When I switch from heat to AC, and AC to heat.

At the same time is turn on/off humidifier as well.
I do the same with a 5" filter. Easy to remember and even though the filter says it could last 1 year, after 6 months it looks like it is ready to be replaced.
Deal Fanatic
User avatar
Oct 12, 2007
8097 posts
6692 upvotes
Ottawa
I make sure that we have a new filter right at the beginning of the cooling season as even a slightly dirty filter can affect how well cool air reaches the rooms in our house furthest from the furnace. We tend to use Merv10 and have no pets.
Deal Fanatic
Dec 27, 2007
5948 posts
3232 upvotes
I was changing it 6 months but it looks perfectly clean so I'm gonna try waiting longer next time.

No pets
No smokers
[OP]
Member
Jul 14, 2017
388 posts
65 upvotes
Ontario
We have all hardwood flooring,no pets,no kids,no smoking,so I think I can be safe by going with Daylight Savings Time to change out our 16x25x5 filter.Last time I think I changed it too early as it still looked fairly clean and mainly changed it only because I had 3 extras on hand, so to be 'safe'. H50
Last edited by Huck50 on Aug 3rd, 2020 6:28 am, edited 1 time in total.
Sr. Member
Jan 14, 2010
686 posts
228 upvotes
Central Ontario
TomLafinsky wrote: You do realize that changing a MERV 8 filter monthly means you are allowing more dust in your furnace than if you were to wait 2-3 months (which is average for a 1" filter). A filter becomes more 'efficient' over time. There is obviously a limit to how efficient it can become. And all this has to be balanced with allowing sufficient air flow.

I would suggest you wait 2-3 months unless you live in an area with above average dust. Filters are supposed to get dirty, to a limit.
I actually don't understand this logic, and can't find any sources that agree with this. Can you enlighten me, thanks?
Deal Addict
Sep 6, 2017
4524 posts
3003 upvotes
cocodc wrote: I actually don't understand this logic, and can't find any sources that agree with this. Can you enlighten me, thanks?
he would rather have the filter flow less causing the fan motor to work harder.
Deal Fanatic
Dec 5, 2009
5756 posts
3589 upvotes
Never changed anything in 6 years. Never had an issue. Sounds like a money grab. You know what they say about a fool and his money.

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