Use distilled or demineralized water, not tap water

Distilled water is the best choice for most humidifiers. It has had minerals removed through boiling and condensation, so it will not leave white dust or mineral buildup inside your machine or on nearby surfaces. Demineralized water works the same way and costs about the same.

Tap water contains minerals like calcium and magnesium. When tap water evaporates in a humidifier, those minerals stay behind. Over time they clog the machine, reduce output, and eventually break it. The white powder that settles on furniture and floors near a humidifier run on tap water is mineral dust — it is harmless to breathe but annoying to clean.

If you live in an area with very hard tap water, mineral buildup happens faster. Even in soft-water areas, distilled water extends the life of your humidifier by months or years.

Key Takeaways

  • Distilled or demineralized water prevents mineral buildup that clogs humidifiers and shortens their lifespan.
  • Tap water leaves white mineral dust on surfaces and inside the machine, even in soft-water areas.
  • Distilled water costs roughly the same as a gallon of milk and is sold at any grocery store or drugstore.
  • Filtered water from a pitcher or faucet filter is not the same as distilled water and will still leave mineral deposits.
  • Bottled drinking water is usually not distilled unless the label says so, and using it costs more than distilled water.

Why filtered water is not enough

Pitcher filters and faucet-mounted filters remove chlorine and some particles, but they do not remove minerals. A filter makes tap water taste better, but a humidifier will still accumulate mineral buildup. The filter removes the wrong things for this job.

Reverse osmosis systems do remove minerals and work similarly to distilled water, but they are expensive to install and maintain. For the cost of running a reverse osmosis system, you can buy distilled water for years.

Bottled drinking water and spring water

Most bottled drinking water is not distilled. Spring water, mineral water, and purified water all contain minerals or have not had them fully removed. Check the label — it should say "distilled" if that is what you are buying. Many brands do not make distilled water at all.

Bottled water costs more per gallon than distilled water at a grocery store. A gallon of distilled water usually runs $0.50 to $1.50, depending on your location and store. Buying bottled water for a humidifier that runs eight hours a day adds up quickly.

Where to buy distilled water

Distilled water is sold at any grocery store, drugstore, or big-box retailer in the cleaning supplies or water section. Walmart, Target, CVS, Walgreens, and most supermarkets stock it. A gallon jug is the standard size and fits most humidifier tanks.

Some people buy distilled water at the same place they fill car batteries or buy ice. Gas stations and car-supply stores sometimes sell it. Online ordering from a grocery delivery service works if you prefer not to carry jugs, though the per-gallon cost may be higher.

How much distilled water you will need

A small humidifier uses about one gallon per day if run continuously. A medium humidifier uses one to two gallons daily. Large or whole-house humidifiers use more. If you run the humidifier eight hours a day instead of 24, you will use roughly one-third as much.

Buying distilled water by the gallon is cheaper than by the case. A case of four gallons costs roughly $4 to $6 at most stores. Buying one gallon at a time costs slightly more per gallon but means less storage space and no waste if you do not use it all.

Cleaning your humidifier if you used tap water

If you have been using tap water and mineral buildup has formed, soak the tank and filter in equal parts white vinegar and distilled water for 30 minutes to an hour. Scrub away loose deposits with a soft brush or cloth. Rinse thoroughly with distilled water before refilling.

For heavy buildup inside the machine, fill the tank with equal parts vinegar and distilled water, run it for a few minutes to distribute the mixture, then let it sit for an hour. Empty it and rinse the tank and all removable parts. Do this once, then switch to distilled water going forward.

Humidifier filters and distilled water

Some humidifiers have replaceable filters that trap minerals and other particles. These filters extend the time between cleanings but do not eliminate the need for distilled water. A filter will clog faster and need replacement more often if you use tap water.

If your humidifier has a filter, check the manual for the recommended replacement schedule. Using distilled water means the filter lasts longer and the machine stays cleaner overall. Some filters are washable and reusable; others are disposable.

Frequently Asked Questions

Can I use rainwater or well water in a humidifier?

No. Rainwater and well water both contain minerals and sediment. Well water is often harder than tap water. Both will cause the same mineral buildup as tap water. Stick with distilled or demineralized water.

Is distilled water safe to breathe in from a humidifier?

Yes. Distilled water is safe to breathe. The mist from any humidifier is just water vapor — the same thing that comes from boiling a pot of water. Distilled water straightforward means the minerals have been removed before it goes into the machine.

What happens if I run out of distilled water and use tap water once?

One fill will not break the machine. But repeated use of tap water causes mineral buildup over weeks and months. If you run out, use tap water once and buy distilled water for the next fill. Do not make it a habit.

Do I need to buy a special brand of distilled water?

No. All distilled water is made the same way — by boiling and condensing. Store brands cost less than name brands and work identically. Buy whatever is cheapest at your local store.

Can I make my own distilled water at home?

Yes, but it takes time and uses energy. Boil tap water in a pot, place a clean bowl inside to catch the condensation, cover with a lid tilted to one side, and let it cool. The water that drips into the bowl is distilled. For a humidifier that uses a gallon a day, buying it is faster and cheaper.