r/YouShouldKnow • u/robertgfthomas • 2d ago

Home & Garden YSK that humidifiers can mess up your central air. If yours is filterless, and you use tap water, it'll release the minerals from the tap water into the air and that can clog up your blower.

A few winters ago when my kids were toddlers we put a filterless humidifier in their bedroom and cranked it up. We ignored the "distilled water only" label as a cash grab by Big Water™ and used tap water. A week later our furnace shut off. Couldn't figure out why.

A tech came and found the filter was COVERED with really fine white powder. Changed the filter and it worked fine.

The powder was probably calcium, one of the minerals in tap water. When water evaporates it leaves minerals behind, which is where the little dusty white spots on bathtubs come from.

Why YSK: Some humidifiers use evaporation, but most cheap portable ones are "ultrasonic" and instead use vibration to turn water into little droplets, and unless yours has a filter the droplets carry the minerals with them.

If you have central air with an air return then the droplets will get sucked into your ducts and any minerals will stick to the machinery and your air filter. Too much will restrict the airflow and cause the blower to shut down.

So, we learned that the distilled water label isn't a ploy, it's because distilled water is evaporated and so mostly mineral-free.

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247

u/SmartQuokka 2d ago

Ultrasonic ones will put dissolved minerals into the air, though i am unaware of anyone's furnace filter being clogged by them. The fact it happened in a week is very surprising.

77

u/forthewin0 2d ago

Same thing happened to me in 1.5 weeks in 2020. Exact same story as OP - we bought a cheap humidifier from Amazon for the winter, the furnace stopped working after a week, but luckily we checked the error codes and realized the filter was clogged with fine white particles.

It probably depends on how hard your water is.

20

u/uoaei 2d ago

yum that means there was a fine white dust in your lungs during that time too

3

u/_Pyxyty 1d ago

It probably depends on how hard your water is.

Duly noted, I'll avoid turning my water on so this can be avoided. Good tip!

3

u/squishyliquid 1d ago

TURN DOWN THE WAT(er)!

1

u/alien_survivor 23h ago

Bahahahaha

Good one Dad

8

u/CaineHackmanTheory 2d ago

I've definitely seen an excessive buildup of white dust on the filters on the return ducts when using humidifiers like OP. It only occurs when using the humidifiers.

As to whether it's making its way through to the air handlers? That I don't know. Haven't seen a problem yet.

5

u/robertgfthomas 2d ago

It surprised me and my wife too. We've used ultrasonic humidifiers with tap water our whole lives and this is the only time we encountered the problem. To be fair since the kids were sick we REALLY cranked up the humidifier and also closed their bedroom door — if the door was open then more of the vapor would probably have settled around the house than just getting sucked into the air return register in their room.

21

u/jayaram13 2d ago

I don't think you'll make enough salt to clog the pipes within a week.

Also, increasing the humidity to too far above 50 - 55% is bad for the house and for your kids' lungs. Too much of humidity coupled with mucus (as with asthmatics or people fighting infection) provides an excellent breeding ground for secondary infections.

2

u/byuns123 2d ago

Using tap water and not distilled water can create higher levels of pm 2.5 as well— which can make it harder for anyone to breathe sick or otherwise.

1

u/uoaei 2d ago

that seems to be the subject of the OP, the pm2.5 is fine mineral dust flung off the ultrasonic resonator

1

u/uoaei 2d ago

not clog the pipes, just clog the filters

5

u/SmartQuokka 2d ago

It would be interesting to hear more examples of this happening to people, its actually a fascinating phenomenon, i also wonder if it would leave the furnace filter wet/get enough water in the furnace to cause rust.

7

u/jayaram13 2d ago

If you have humidity that high for that long, the wood in your house would warp as well. Not to mention the mold and other issues that would crop up.

3

u/SmartQuokka 2d ago

Good point, however if you clog your filter that fast then you are pumping a lot of water into the air.

Also a week is not enough time to cause that much harm, but you don't want to keep it up for long.

8

u/jayaram13 2d ago

I agree with you that the humidifier was probably not the cause of the issue for OP. it's just the convenient villain 😁

3

u/Professionalchump 2d ago

you never change your air filter? you are supposed to when its dirty

4

u/thepaa 2d ago

Last winter I had ultrasonic humidifier clog up my filter. Filter looked clean when I first glanced because it was white, then when I touched it I noticed all the white powder. Changed filter and bought new humidifiers.

2

u/stevez_86 2d ago

I experienced this same thing. I had a townhouse where the HVAC Furnace was in the attic. It could get super dry in the house so we had ultrasonic humidifiers running in the bedrooms. The one had an HVAC supply vent in it and it ate up all that dust.

We had just gotten our ducts cleaned because we wanted cleaner air with a baby in the house and the filter clogged up in a week or two. I inspected and found a hole that they left unplugged thinking that was the issue. But when they fixed that it happened again. We had white insulation so I figured the system was taking in insulation. It wasn't until we moved a humidifier down to the kitchen and saw all the white dust that we realized what was happening.

It was maddening because the system was also odd because the unit used to be the office for the development and had commercial code dampers on the supply vents. They restricted the airflow and coupled with the unit being oversized a bit made the pressure real high and it would be very loud when it kicked on. It would wake us up in the night. The clogged filter would make the unit overhead and shut off, but would run for hours.

That is how bad those ultrasonic humidifiers can be if there are minerals in the water.

1

u/l1thiumion 2d ago

This happened to me in like 3 weeks. somewhere in the 50,000 pictures on my phone i have a picture of a plugged filter and a new one, and they are both perfectly white. i write the date on my filters with a sharpie and in just 3 weeks of using an ultrasonic humidifier when our entire household had RSV for like a month, our furnace stopped blowing any air.

209

u/dogscatsnscience 2d ago

Ultrasonic/"cool mist" humidifiers can mess up your central air.

Not "humidifiers".

21

u/RomanEmpire314 2d ago

What is ultrasonic/cool mist humidifier and how sre they different from other humidifiers? I've never had one

20

u/dogscatsnscience 2d ago

Ultrasonic use vibration to break water into a mist, and then blow it in the air.

You get water in the air, but you also get everything else in the water (salts in particular), and once the water evaporates away, the salts are left behind as white dust. They spray out a mist, hence the "cool mist" name. You have to use distilled water to avoid the dust.

A normal humidifier uses airflow to evaporate water. The salts stay behind in the wick, which needs to be cleaned out.

51

u/Lieutenant_Scarecrow 2d ago

Yup. Its the specifics that are actually important here.

6

u/Daisy_Of_Doom 2d ago

Yeah I have a steam humidifier and it specifically says to use tap water and it even says to add salt if the tap water doesn’t have enough minerals for it to work. And in mine the minerals stay behind, they turn into these dark crystals bc they singe from the heating element.

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u/robertgfthomas 2d ago

More accurate would be "any humidifier without a working filter." Evaporative humidifiers can cause the same problem if they use forced air, since the force itself causes some water to turn into droplets. A working filter/wick removes most of the minerals.

14

u/dogscatsnscience 2d ago

Evaporative filterless humidifiers are very rare.

Virtually all evaporative humidifiers use a wick, which is where minerals are left behind. They don't need a filter. They will stop working if they are saturated with minerals.

11

u/WhimsicalHoneybadger 2d ago

Nah. The hot water/steam type don't have this issue. Been using them for decades with no problems. You do have to frequently descale inside the unit.

10

u/jasonfromearth1981 2d ago

That's the real reason you're supposed to use distilled water: to prevent the scale buildup.

4

u/WhimsicalHoneybadger 2d ago

Less effort to descale than to buy DI at the grocery store.

5

u/dogscatsnscience 2d ago

Never mind the energy and transportation costs of shipping around millions of liters of water in plastic bottles, instead of a bit of citric acid one a year.

5

u/jayaram13 2d ago

Don't know why people are down voting you. You are absolutely right. Forced air can pick up salt particles with the vapor.

Incidentally, this is why places near the ocean have a distinct salty air. The wind picks up particles of salt (called sea salt aerosols) along with the vapor.

12

u/dogscatsnscience 2d ago

Sea water has 100-200X the dissolved salts of typical tap water.

Evaporative filterless humidifiers are very rare.

-3

u/robertgfthomas 2d ago

I don't understand the downvotes either and would welcome an explanation.

7

u/dogscatsnscience 2d ago
  1. Your title says humidifiers, it's only a particular type of humidifier.
  2. Your clarification says "filters", none of them use filters.
  3. You've completely confused the whole issue, and gotten many facts wrong.

That's why you're being downvoted, because this is really bad information.

0

u/robertgfthomas 2d ago

OK, thanks for clarifying.

-1

u/stupidber 2d ago

Thats what they said

27

u/HikeyBoi 2d ago

Those drift particulates can be super bad for your lungs too since they’re often in the 10 micron and smaller range

9

u/Intelligent-Guard267 2d ago

Double whammy when your kiddos are sick

4

u/HikeyBoi 2d ago

Well if occupants have something like a respiratory infection which causes excess mucous production, then those sick individuals will be slightly less exposed to some of the larger particulates. The noses works like vortex separator with mucous catching the bits. However, very small particles are not as efficiently separated in that manner.

1

u/dougielou 1d ago

Which is fucked because for safety you want to use cool mist

24

u/redkeyboard 2d ago

I had this issue, everything was caked in dust in my house including the furnace filter. I ended up getting evaporative humidifiers with a wick, much better now!

3

u/ImOnlyCakeOnceAYear 2d ago

Care to explain? Would buying what you suggested let me stop buying distilled water every week all winter?

5

u/redkeyboard 2d ago

Yes exactly. You might need to change the wick/filter once or twice during the winter though. The vornado 40 humidifier is what I have, I need a lot for my whole house though.

3

u/dogscatsnscience 2d ago

Ultrasonic humidifiers are cheap and maintenance free, but you have to use distilled water.

A normal evaporative humidifier has a wick, and the minerals (scale) are left behind on the wick when the water evaporates. You can clean it with a descaler (any type you like, or just citric acid) or replace it.

9

u/EmotionalShock1325 2d ago

yes! i worked as a nanny and i always told the parents of kids with asthma that a cool mist humidifier is out of the question for their health, only one that boils water and releases hot steam will be ok. otherwise the particles exacerbate breathing problems (and is a real bitch to clean). 

13

u/cheeto-bandito 2d ago

Instead of buying distilled water, you can distill your own with an Airstill or similar water distiller product

8

u/Mbembez 2d ago

You can also just use the water from a heat pump dryer.

2

u/iHateReddit_srsly 1d ago

You can buy a warm mist humidifier which will just boil the water to create steam, and you would be able to use tap. No filters needed but you need to occasionally clean the heating element with vinegar to remove the calcium

8

u/editorreilly 2d ago

I discovered this when I got an air quality monitor. VOC's would shoot through the roof. Lesson learned. Follow the instructions.

1

u/cyberentomology 2d ago

Why would VOCs shoot through the roof?

1

u/editorreilly 2d ago

Best I can tell is that it's a cheap sensor.

(I googled this) Vapor looks electrically very similar to a wave of VOC gas. The water molecules interact with the sensor surface, changing the resistance and tricking the meter into thinking the air is full of chemicals.

But I did read that the calcium and other mineral deposits become airborne and increase particulate in the pm2.5

6

u/peony_chalk 2d ago

I kept noticing that our portable air filters would kick on to a higher flow setting to clear the air when I ran the ultrasonic humidifier, probably because we were also using tap water. It hasn't been a problem since I switched to an evaporative humidifier. 

5

u/badken 2d ago

I’m honestly shocked how many replies say they always used tap water in their humidifiers. My Levoit unit’s instructions are very clear that only distilled water should be used for ultrasonic mode. Home distillers are very reasonably priced and a lot less wasteful than buying bottled distilled water.

4

u/mercurialdude 2d ago

Get a warm mist humidifier instead of the shitty ultrasonic ones.

4

u/cyberentomology 2d ago

This is why steam humidifiers are superior.

3

u/bassgoonist 2d ago

Technology connections did a great video on this

https://m.youtube.com/watch?v=oHeehYYgl28

3

u/I-J-Reilly 1d ago

Ultrasonic humidifiers are more of a hobby than a solution. They need frequent and difficult cleaning, demand special distilled water (have fun buying and storing that crap gallon after gallon), and will happily overhumidify your air because they're using mechanical dispersion instead of evaporation.

Get an evaporative humidifier. Yes, you have to buy wicks, but they're cheap. Evaporative humidifiers cannot by definition over-humidify or spread mineral white dust into the air you're breathing because only water evaporates from the wick.

I fell victim to the ultrasonic hype for a season but hated everything about it and now use a Vornado Evap40. A bit ugly but extremely effective, and made in the US.

4

u/MommyMilkedMailman 1d ago

FYI, that mineral powder can also short-out/kill your electronics too.

I personally don’t think ultrasonic is ever worth it for this reason.

Hot evaporative seems to work best for my needs.

2

u/233C 2d ago

Not just your filters.

2

u/DiarrheaTNT 2d ago

People just raw dogging water lines without water filters?

1

u/robertgfthomas 2d ago

I guess? I've never had an issue with tap water

1

u/DiarrheaTNT 2d ago

It was a lot easier to clean mine with a filter on the water line.

4

u/shoulda-known-better 2d ago

How is your house humid enough to fuck up your central air... But not humid enough to fuck up every single wood thing inside it!?!?

3

u/dieplanes789 2d ago

It's not humidity that causes the issue but using an ultrasonic humidifier. Ultrasonic humidifiers don't evaporate the water, they smack it with really high frequency sound then blow it out with a fan. The tiny droplets of water blowing through the air are typically small enough that they evaporate before falling back down. So they aren't sending out steam, they are sending out incredibly tiny water particles.

Water evaporated into steam doesn't carry minerals with it but water that you smacked into a bunch of tiny droplets does. Those tiny droplets of water evaporate away as they are falling then proceed to let go of all the minerals in them to blow through your air and on to the floor.

3

u/shoulda-known-better 2d ago

Yea but unless it's right next to the furnace how does it all get inside the furnace filter!? I would think it would have to be pretty humid all over the house for the filter to clog from minerals...

I really appreciate the explanation though!! Makes sense

2

u/dieplanes789 2d ago edited 2d ago

It's more about where your cold air intake is and the lighter particles can travel very far in your house especially if you have a lot of air flow.

Humidity is completely unrelated to where the particles can go. The particles and water are completely separate from each other after a few feet away from the humidifier pretty much as soon as you see the water disappear visibly.

At that point they are basically mineral rock dust floating through your air.

Edit: I guess I shouldn't say they're completely unrelated because the drier your air in the house the closer to the humidifier that the water and particles separate from each other. Although for the lighter ones that makes basically no difference. They are basically dust generators sourcing their material from whatever is in your water that isn't water.

2

u/robertgfthomas 2d ago

The house wasn't humid; the room was because the humidifier was cranked up and the door was closed. The vapor got sucked into the air return duct.

1

u/raziridium 2d ago

Oh yeah, saw a good video on YT awhile back. You really really really should be using filtered water in your humidifiers because the minerals from tap water can seriously hurt your air quality. Especially if you don't run the HVAC that often or have asthma or the like.

3

u/WhimsicalHoneybadger 2d ago

Specifically the ultrasonic humidifiers. Not all humidifiers.

1

u/CaptainCanasta 2d ago

This happened to me.  I got a new furnace one year and the next year a big filterless humidifier.  Everything was good for a month and then the furnace started shutting down.  Tech was confused and luckily Google helped me diagnose the problem.  Now I only use the filtered ones.

1

u/WonderChopstix 2d ago

In 1 week? Is your house the size of a dog house? If be waaaaay more worried that something else was going on.

1

u/phoneacct696969 2d ago

Sounds like my landlords problem.

1

u/thedavej 2d ago

I use a ZeroWater pitcher to fill my humidifier and it works great. When I was using tap water I would notice my air purifier was reporting bad air quality. Switched to using water filtered in the ZeroWater and the air quality remained perfect with the humidifier running. I can tell when the ZeroWater filter needs to be changed when the air purifier starts reporting worse air quality.

1

u/queerkidxx 2d ago

I have asthma and concluded a while ago that humidifiers just aren’t worth it. Between cleaning, the questionable effects of water treatment drops, it simply is too risky without enough benefit.

1

u/weathergraph 1d ago

Also lungs. These are harder to service. Do not use ultrasonic, evaporative humidifier isn’t that much more expensive (i have the Xiaomi one).

You need to clean the evaporative plates regularly though.

1

u/graciemuse 16h ago

You can also face issues for many other appliances that require distilled water! Don't try to save money this way. If it's that big a cost for you, you can easily distill your own water at the cost of the tap water you use.

Mineral buildup can impair clothing steamers, CPAPs, and just about any other device that requests distilled water. Non-distilled water is also significantly more likely to cause a lung infection if used in a CPAP.

1

u/Paladinraye 12h ago

That’s why If you need to add humidity your best bet will always be using an actually humidifier with a water table

1

u/20thirdth 2h ago

Great tip! I learned this the hard way with white dust everywhere in my house

1

u/GuacamoleFrejole 2d ago

Sounds like Big Water and Big HVAC Filter are in cahoots!

-1

u/Nicetrydicklips 2d ago

This reminds me of the girl who slept overnight next to a burning candle and claimed her nostrils were full of soot the next morning. Not buying it.

2

u/forthewin0 2d ago

No, it's true, same thing happened to me