Use distilled or demineralized water, not tap water

Distilled water is the safest choice for most humidifiers. It has been boiled and condensed to remove minerals, bacteria, and other particles that tap water contains. When you use distilled water, you avoid the white mineral dust that builds up inside the tank and comes out into your air.

Demineralized water works the same way — minerals have been removed through a different process. Both cost roughly the same and are sold in gallon jugs at any grocery store, drugstore, or supermarket in the cleaning supplies aisle, usually near the laundry detergent.

Tap water contains minerals like calcium and magnesium. When the humidifier heats or vibrates the water, these minerals separate and either coat the inside of the machine or spray into the air as white dust. Over time, mineral buildup clogs the humidifier and shortens its life.

Key Takeaways

  • Distilled or demineralized water prevents mineral buildup inside the humidifier and keeps white dust out of your air.
  • Tap water leaves mineral deposits that clog the machine and reduce how long it lasts.
  • Bottled water labeled "purified" or "spring" still contains minerals and will cause the same problems as tap water.
  • Distilled water costs a few dollars per gallon and is sold in the cleaning supplies section of most stores.
  • If you use tap water regularly, you will need to clean the humidifier more often and replace parts sooner.

Why tap water damages humidifiers

Tap water varies by location, but most contains dissolved minerals. In areas with hard water — where mineral content is high — the problem is worse, but even soft tap water has enough minerals to cause buildup over weeks of use.

When a humidifier releases water into the air, the minerals stay behind. In ultrasonic humidifiers, which vibrate water into a fine mist, minerals spray directly into your room as white powder. In warm-mist or steam humidifiers, minerals coat the heating element and the inside walls of the tank, making the machine work harder and fail sooner.

The buildup also creates a place for mold and bacteria to grow. A humidifier clogged with mineral deposits becomes less effective and may stop working entirely after a few months of daily use.

Distilled water versus demineralized water

Both remove minerals, but through different methods. Distilled water is boiled until it turns to steam, then cooled back into liquid — the minerals do not evaporate and are left behind. Demineralized water passes through a chemical filter that strips out minerals. The end result is nearly identical for humidifier use.

Cost is about the same: a gallon of distilled water typically runs $1 to $3 depending on your location and store. Demineralized water may be slightly cheaper in some areas. Either one will last several days in a humidifier, depending on the tank size and how often you run it.

Some people use reverse-osmosis water from a home filter system, which also removes minerals. If you already have one installed, that water works just as well as store-bought distilled water.

Why "purified" and "spring" water do not work

Bottled water labeled "purified" or "spring" has been filtered for taste and safety, but minerals remain. Purified water removes some contaminants but leaves minerals intact. Spring water comes from a natural source and contains whatever minerals were in that source.

Neither type is processed enough to prevent mineral buildup in a humidifier. They will cause the same white dust and clogging as tap water, even though they cost more. Save the bottled water for drinking and use distilled water for the humidifier.

How often to refill and what happens if you skip distilled water

How often you refill depends on tank size and how many hours per day you run the humidifier. A 1-gallon tank on continuous use may need refilling every one to three days. Check the water level daily and refill when it drops below the fill line.

If you use tap water instead of distilled water, you will see white mineral dust on surfaces near the humidifier within a week or two. The humidifier itself will become harder to clean, and the heating element or vibration mechanism will wear out faster. Some machines stop working after two to four months of tap water use, while distilled water can keep them running for years.

Where to buy distilled water and storage tips

Distilled water is sold in gallon jugs at grocery stores, drugstores, Walmart, Target, and most supermarkets. Look in the cleaning supplies aisle or near the laundry section. Some stores also stock it near bottled drinking water. A single gallon costs between $1 and $3 and lasts several days depending on your humidifier size.

Store distilled water in a cool, dry place away from direct sunlight. An unopened jug stays good for months. Once opened, use it within a week or two — distilled water can absorb minerals and bacteria from the air if left sitting. Do not store it in the humidifier tank between uses; empty the tank after each use to prevent mold growth.

Cleaning your humidifier when mineral buildup happens

Even with distilled water, humidifiers need regular cleaning. Empty the tank after each use and wipe the inside with a soft cloth. Once a week, soak removable parts in equal parts white vinegar and water for 15 to 30 minutes to dissolve any mineral deposits that have formed.

If you have been using tap water and mineral buildup is heavy, soak the tank and parts overnight in vinegar. Use an old toothbrush to scrub stubborn deposits. Rinse everything thoroughly with distilled water before refilling. If the heating element or vibration mechanism is clogged and will not come clean, the humidifier may need replacement.

Frequently Asked Questions

Can I use rainwater or well water in a humidifier?

No. Rainwater collects bacteria and particles from the air and roof. Well water often has more minerals than tap water, depending on your location. Both will cause faster buildup and clogging than tap water. Stick with distilled or demineralized water.

Is it safe to add essential oils or medicine to humidifier water?

Check your humidifier manual first. Most manufacturers say not to add anything except water. Essential oils and medications can damage the machine, clog the filter, and create buildup. Some humidifiers have a separate medicine cup designed for this purpose — use that instead of adding anything to the water tank.

What if I cannot find distilled water at my store?

Demineralized water is a direct substitute and usually available at the same location. If neither is in stock, ask the store when they restock. You can also order distilled water online for delivery. In the meantime, tap water will work but will require more frequent cleaning of the humidifier.

Do I need to use distilled water in a cool-mist humidifier?

Yes. Cool-mist humidifiers use ultrasonic vibration to spray water into the air, so minerals spray directly into your room as white dust. Distilled water prevents this. Warm-mist humidifiers also need distilled water to prevent mineral buildup on the heating element.

How much does it cost to use distilled water instead of tap water?

A gallon of distilled water costs $1 to $3 and lasts several days depending on humidifier size and use. For a humidifier running eight hours a day, expect to spend $5 to $15 per month on distilled water. This is far less than replacing a humidifier that has failed due to mineral damage.