The fastest way to get distilled water is to buy it at a grocery store or drugstore
Distilled water sits on the shelf next to bottled drinking water in most supermarkets, drugstores, and big-box retailers. A gallon typically costs between $1 and $3, depending on the brand and where you shop. You do not need a special trip — it is stocked in the same aisle as other water products, usually near the pharmacy section or in the cleaning supplies area.
Walmart, Target, CVS, Walgreens, and most local grocery chains carry it year-round. Some stores stock multiple brands; store brands are usually cheaper than name brands like Aqua Distilled or Culligan and work just as well in a humidifier. Buy a gallon or two at a time so you have it on hand when your tank runs low.
If you use your humidifier daily, buying distilled water regularly adds up. A household running a humidifier eight hours a night might use two to four gallons a week, which means $8 to $12 monthly just for water. For that reason, many people make their own distilled water at home instead.
Key Takeaways
- Distilled water is sold at grocery stores, drugstores, and big-box retailers for $1 to $3 per gallon and is usually stocked near bottled water or the pharmacy section.
- You can make distilled water at home using a pot, a heat source, a bowl, and ice, which costs only a few cents per gallon.
- Tap water left sitting in a humidifier tank builds up mineral deposits that clog the machine and reduce output, so distilled water is worth the cost or effort.
- Store-bought distilled water lasts indefinitely in a sealed container, but homemade distilled water should be used within a week or two to prevent bacterial growth.
How to make distilled water using boiling and condensation
The simplest method uses a pot, a heat-safe bowl, and ice. Fill a large pot halfway with tap water and place a heat-safe bowl in the center so it floats or sits on a trivet — the bowl should not touch the bottom. Cover the pot with a lid upside down so the dome points downward, then bring the water to a boil.
As steam rises and hits the cold lid, it condenses into droplets that run down the dome and drip into the bowl below. After 15 to 20 minutes of boiling, you will have collected distilled water in the bowl. Let it cool, pour it into a clean container, and store it in the refrigerator. This method produces about one cup of distilled water per 20 minutes of boiling, so plan accordingly if you need a full gallon.
To speed up the process, place ice on top of the upside-down lid. The colder surface makes condensation happen faster. You can also use a glass bowl inside the pot so you can see how much water has collected without lifting the lid.
Using a water distiller machine for larger quantities
If you run a humidifier constantly or have multiple machines, a countertop water distiller pays for itself within a few months. These machines heat water and collect the condensed steam, producing one to five gallons per cycle depending on the model. Prices range from $50 to $200, and they run on electricity.
A distiller takes two to four hours per cycle and produces water that is ready to use when ready. You straightforward fill the tank with tap water, turn it on, and collect the distilled water from the output container. Most models have an automatic shutoff when the cycle is complete. This is the most hands-off method if you use distilled water regularly.
Distillers also remove more contaminants than the boiling method because the water is heated to a higher temperature and the condensation process is more thorough. If mineral buildup in your humidifier has been a recurring problem, a distiller may be worth the investment.
Why tap water damages humidifiers and why distilled water matters
Tap water contains minerals like calcium and magnesium that do not evaporate when water turns to steam. Instead, they accumulate inside the humidifier tank and on the heating element, forming a white or tan crust called scale. Over time, this buildup clogs the nozzle, reduces mist output, and can damage the machine permanently.
Distilled water has had these minerals removed during the distillation process, so it leaves no deposits behind. Using distilled water extends the life of your humidifier and keeps it running at full power. If you have already used tap water and see white buildup inside the tank, you can clean it with white vinegar and a brush, but switching to distilled water prevents the problem from happening again.
Some humidifiers come with demineralization cartridges that trap minerals as water passes through. These cartridges need to be replaced regularly and add to the cost of running the machine. Using distilled water from the start eliminates the need for these cartridges on many models.
Storing distilled water so it stays clean and ready to use
Store-bought distilled water in a sealed bottle lasts indefinitely if kept in a cool, dark place away from direct sunlight. An unopened gallon can sit in a cabinet for years without spoiling. Once you open it, use it within a few weeks and keep the cap tightly closed between uses.
Homemade distilled water should be used within one to two weeks because it has not been treated to prevent bacterial growth the way commercial distilled water is. Store it in a clean, sealed container in the refrigerator. If you notice any cloudiness, odor, or visible particles, discard it and make a fresh batch.
Do not store distilled water in direct sunlight or in a warm location, as heat and light can allow bacteria to grow. A kitchen cabinet or pantry shelf works well. Label homemade distilled water with the date you made it so you know when to replace it.
Comparing the cost of buying versus making distilled water
Buying distilled water costs $1 to $3 per gallon. If you use two gallons per week, that is $8 to $24 monthly. Over a year, that adds up to $96 to $288 just for water.
Making distilled water at home costs only the electricity to boil water, which is roughly $0.10 to $0.25 per gallon depending on your local electricity rates and how efficient your stove is. A countertop distiller costs $50 to $200 upfront but produces water for about $0.15 to $0.30 per gallon after the initial investment is recovered.
For light use — a humidifier running a few hours a week — buying distilled water is simpler and cheaper. For daily or heavy use, making your own distilled water saves money over time. Calculate your own usage: if you use more than one gallon per week, a distiller or regular boiling method will save you money within the first year.
Frequently Asked Questions
Can I use bottled drinking water in my humidifier instead of distilled water?
No. Bottled drinking water still contains minerals, just fewer than tap water. It will still leave deposits in your humidifier over time. Distilled water is the only type that has had minerals removed through the distillation process, so it is the only choice that prevents buildup.
What if I boil distilled water — does that make it even cleaner?
Boiling distilled water does not make it cleaner or better for your humidifier. Distilled water is already as pure as the distillation process can make it. Boiling it again serves no purpose and wastes energy. Use it straight from the bottle or container.
Is rainwater or melted snow a good substitute for distilled water?
No. Rainwater and melted snow contain dust, pollen, and other particles that settle during collection. They also contain minerals from the air and ground. Neither one is distilled, so both will leave deposits in your humidifier. Stick with distilled water or water you have distilled yourself.
How do I know if my humidifier has mineral buildup from tap water?
Look inside the tank and on the heating element for white, tan, or chalky deposits. You may also notice that the mist output has decreased even though the tank is full, or that the machine makes unusual sounds. If you see buildup, clean it with white vinegar and a soft brush, then switch to distilled water going forward.
Can I use a water filter pitcher to make tap water safe for my humidifier?
No. Water filter pitchers remove some contaminants and improve taste, but they do not remove minerals the way distillation does. Filtered tap water will still leave deposits in your humidifier. Only distilled water or water you have distilled yourself will prevent mineral buildup.