Somewhere between the last real heat and the first cold morning, your furnace switches jobs without asking. Before it does, there's a two-minute check worth doing now, while the utility closet is still easy to get to and nobody's chasing you about the thermostat yet.
Below: what a clogged filter actually costs you, the one MERV number worth knowing, and a free fix for a slow bathroom drain.
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What a Clogged Furnace Filter Actually Costs You
Your furnace filter has exactly one job. It catches dust, pet hair, and lint before any of it reaches the blower motor and the coils behind it. When the filter is caked shut, it can't do that job, and the system pays for it every time it runs, not just on the coldest night of the year.
ENERGY STAR is blunt about what that actually costs you. Its own maintenance guidance says a dirty filter slows the air moving through your house, which forces the blower to work harder to push the same amount of air around.
Same comfort, more electricity. Skip it long enough and the dust that should have been caught starts building up inside the system instead, the kind of buildup that leads to a real repair bill or an early system failure.
The good news: the fix takes less time than finding the remote, and most people are standing right next to the filter without knowing it. September is a good time to get ahead of it, since the furnace hasn't kicked on for real yet and there's no urgency, just an easy few minutes before the season actually needs the thing to work.
A recurring phone reminder does the remembering for you, so you're not left guessing every fall. Set one for the first of every other month, and by the time winter actually arrives, the filter's already been swapped instead of sitting there working overtime.
Find it. Most residential filters live in one of three spots: a slot on the return-air duct near the furnace, a slot built into the furnace cabinet, or a grille set into a hallway wall or ceiling.
Check the size and the arrow. The exact size, something like 16x25x1, is printed right on the cardboard frame. There's also a small arrow on that same frame, and it has to point toward the furnace, not away from it.
Swap it. Slide the old one out, slide the new one in, arrow facing the same direction the old one did.
Write the date on the frame. A marker line on the edge tells you, or whoever swaps it next, exactly when the clock starts again. Most homes are fine checking every 60 to 90 days, sooner with pets in the house.
Not sure it's time yet? Hold the old filter up to a light. If you can't see light coming through it, it's stopped filtering and started blocking.
One more two-minute check while you're standing in the utility closet. Daikin recalled roughly 4,600 Amana-brand through-the-wall air conditioners and heat pumps on September 3 over a snubber circuit that can catch fire. If you own one of those units, it's worth confirming yours isn't on the list before you move on to the filter. The remedy is a full refund, not a repair.
The filter itself is the cheapest part of all this. Scroll down for the exact one we'd buy, and what it actually costs right now.
The Free Fix For A Slow Bathroom Drain
Image: Wikimedia Commons (public domain)
Kitchen sinks clog with grease. Bathroom sinks clog with hair. A slow bathroom sink almost never means a clog deep in the pipe: it usually means hair wrapped around the pop-up stopper, sitting exactly where you can reach it without any tools.
Find the pivot rod. Look under the sink where the drain pipe meets the wall behind it. There's a small horizontal rod threaded into the back of the drain assembly, connected up to the stopper above.
Loosen it and pull the stopper straight up. Unscrew the nut holding the pivot rod in place, slide the rod out, then lift the stopper straight out of the drain opening.
Pull the clump off by hand. A glove makes this a lot less unpleasant. This is almost always exactly where the water is getting stuck, not further down the pipe.
Rinse it, replace it, reconnect the rod. Drop the stopper back into the drain, slide the pivot rod back through its hole, and tighten the nut.
If the sink is still slow after this, the clog is further down than the stopper reaches, and this trick won't fix it. That's a job for a real drain snake, or a call to a plumber, not another home remedy. If you'd rather skip taking anything apart, a flexible plastic zip-style drain tool from any hardware store slides past the stopper and pulls the hair straight out.
What A MERV Rating Actually Means
MERV stands for Minimum Efficiency Reporting Value. It's the industry-wide scale, developed by ASHRAE (the engineers' group that writes HVAC standards), that rates how well a filter catches particles between 0.3 and 10 microns, according to the EPA. The higher the number, the smaller the particle it catches.
TLDR: MERV 8 catches basic household dust. MERV 11 adds pollen, mold spores, and pet dander. MERV 13 filters smoke and finer particles.
The EPA's own guidance says that if you're going to upgrade, aim for at least a MERV 13, or as high a rating as your system's fan and filter slot can actually accommodate, and to check with an HVAC technician if you're not sure where that ceiling sits.
That's worth taking seriously. A higher-MERV filter is a denser filter, and a denser filter makes the blower work harder to pull air through it: the same core problem a dirty filter causes, just built into a brand-new one. Most standard residential systems handle a MERV 11 filter without any issue, which is why that's the pick below. Jumping straight to 13 on an older or smaller system is exactly the kind of thing worth a quick call to a technician first, not a guess.
Some higher-end systems use a washable filter instead of a disposable one. If yours does, the same MERV logic applies, you're just hosing it off instead of tossing it in the trash.
One more mix-up worth clearing up: MERV isn't the same scale as HEPA. A true HEPA filter is a much denser standard built for air purifiers and hospital rooms, and most home furnace blowers can't pull air through one at all without straining. MERV is the number that actually applies to the slot in your own ductwork.
The Filter We'd Actually Point You To
Filterbuy's 16x25x1 MERV 11 pleated filter is the one we'd grab off the shelf. It's a real step up from the bargain-bin MERV 8 filters most hardware stores push (it catches the pollen, mold spores, and pet dander an 8 lets straight through), without the added airflow resistance a MERV 13 can cause on an older system.
Check your own filter's size before you order anything. The three numbers stamped on the cardboard frame, something like 16x25x1, give you the length, width, and depth in inches. Filterbuy sells this same filter line in dozens of sizes, so match yours first. It's the single most common mistake people make ordering filters online.
One filter runs $22.49 at the time of writing. A 2-pack drops that to $13.49 each ($26.98 total), which is worth doing anyway since you'll want a spare on hand for the next swap in 60 to 90 days rather than remembering to reorder at the worst moment. And a 6-pack - what we linked to - is $90 for 6 from Amazon. Filterbuy themselves has it for cheaper and you can set up auto delivery.
This is a MERV 11, not a MERV 13. For most systems that's the right call, for the airflow reasons above, but if your HVAC tech has already confirmed your system handles higher-efficiency filters without a problem, the same product line goes up to a 13 as well.
Delivery typically runs 3 to 5 business days, so if your current filter already looks due, order now rather than waiting until the exact day you want to swap it. There's no subscription trap either: it's a one-time purchase, though Filterbuy also offers a recurring-delivery option if you'd rather never think about it again.
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How old is the filter in your furnace right now?
That's the whole list for this week: a filter that's cheaper to swap than to ignore, a MERV number worth actually knowing, and a slow bathroom drain fixed without a single tool or a call to anyone.
If this saved you a trip to the hardware store for the wrong size filter, forward it to whoever in your house keeps saying "we should really check that."
See you Thursday, with more of the same.
The Home Wire
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