What If I Don’t Have Distilled Water for My CPAP?

Running out of distilled water does not mean you should skip your CPAP therapy for the night. You have several workable options: using the machine without water in the humidifier chamber, using tap water as a short-term substitute, or boiling and cooling tap water before adding it. Each approach carries different trade-offs in comfort and equipment maintenance, but none of them should keep you from wearing your mask. The real risk with CPAP is not what happens on the occasional night without distilled water; it’s what happens when people stop using the machine altogether because they think they have no choice.

Running Your CPAP Without Water

Every CPAP machine with an integrated humidifier can run with an empty water chamber. The humidifier is a comfort feature, not a medical requirement. Simply leave the chamber empty (or remove it if your machine allows) and turn the humidifier setting off or down to zero. The device will deliver the same therapeutic pressure to keep your airway open.

The trade-off is dryness. Heated humidification reduces upper airway symptoms like nasal congestion, dry nose, dry mouth, sneezing, and stuffiness.¹ Without it, the steady flow of room-temperature air through your nose can dry out your nasal passages and throat, especially if you breathe through your mouth during sleep. A study comparing CPAP with and without controlled heated humidification found that mouth dryness improved with humidification within the first two nights and continued improving over four weeks.² So running dry for a night or two is uncomfortable for many people, but it is not harmful.

If you regularly find yourself without distilled water, the dryness may chip away at your willingness to use the machine. Research consistently shows that heated humidification is associated with a small increase in CPAP usage hours, though it does not dramatically change how sleepy people feel or how satisfied they report being with treatment.³ The takeaway: humidification makes CPAP more tolerable, especially for people prone to nasal symptoms, but skipping it short-term is always better than skipping your therapy.

Using Tap Water as a Temporary Fix

Most CPAP manufacturers recommend distilled water, and for good reason: it leaves no mineral deposits behind when it evaporates. But the concern about tap water is often misunderstood. The primary issue is not that tap water will immediately make you sick. In a convection-type heated humidifier (the kind built into most modern CPAP machines), one study found that bacteria and dissolved substances in the water were not transported into the airstream and would not be deposited in the lungs, leading the researchers to conclude that non-sterile tap water is probably a safe alternative in that humidifier type.⁴

That finding is worth putting in context. It applies to a specific humidifier design and addresses whether aerosolized bacteria from contaminated water can reach your lungs in a single session. It does not mean tap water is harmless over the long haul. Repeated use of tap water leaves behind calcium and magnesium scale inside the chamber, which can become difficult to clean and may eventually damage the humidifier or create textured surfaces where biofilm and bacteria gain a foothold. If you use tap water for one night because you ran out of distilled, you will likely wake up fine and just need to clean the chamber more thoroughly in the morning. If you use tap water habitually, you will be scrubbing mineral crust off your equipment regularly and potentially shortening its lifespan.

Boiled Water and Other Alternatives

A CDC-affiliated survey on home medical device water use noted that boiled and cooled water is an acceptable alternative to distilled water for respiratory devices, alongside sterile water.⁵ Boiling kills bacteria and other pathogens, which addresses the infection side of the equation. It does not, however, remove dissolved minerals. When the water evaporates in your CPAP chamber, those minerals stay behind just as they would with unboiled tap water. So boiled tap water is a reasonable middle ground: it reduces microbial risk while still leaving some mineral residue to clean up.

A few other water types people sometimes consider:

Bottled spring water: This is essentially tap water from a different source. It contains minerals and is not sterile. It will leave deposits just like your home tap water would.
Filtered water: Standard pitcher filters or fridge filters reduce chlorine taste and some contaminants but do not remove dissolved minerals or sterilize the water. They are a marginal improvement over plain tap water for CPAP purposes.
Bottled “purified” or “drinking” water: This varies enormously by brand. Some are essentially distilled; others have minerals added back for taste. Check the label. If it says “distilled” or “steam-distilled,” it works. If it says “purified with minerals added,” treat it like tap water.
Softened water: Water softeners replace calcium and magnesium with sodium. The water still contains dissolved solids and can leave a film. It is not a good substitute for distilled.

If you travel frequently and worry about finding distilled water, some CPAP users carry a small supply or buy gallon jugs at grocery stores and pharmacies, which stock distilled water in most countries. In a pinch abroad, bottled water labeled “distilled” or “demineralized” works identically to the gallon jugs back home.

The Actual Infection Risk From Dirty Equipment

When clinicians worry about CPAP water quality, the concern is less about a single night of tap water and more about what happens when water sits in a warm, dark humidifier chamber for days or weeks without being changed or cleaned. Stagnant water in a heated chamber is an inviting environment for bacteria. In laboratory testing, bacteria placed in CPAP humidifier water were recovered in the breathing tubes in 9 of 11 tests, with colony counts ranging from tens to thousands, demonstrating that pathogens in contaminated humidifier water can reach the tubing.⁶

Case reports illustrate what this looks like in real life. One patient developed Legionella pneumonia traced back to her CPAP equipment, which had not been cleaned properly. Investigators determined that the bacterium likely grew in her mask, tubing, and humidifier.⁷ In another case, a man with chronic lung disease presented with worsening breathing problems and was found to have Pseudomonas aeruginosa pneumonia. He admitted to poor CPAP maintenance and had visible green-colored growth on his mask consistent with Pseudomonas colonization.⁸ Pseudomonas is a waterborne organism that thrives in humid environments and is especially dangerous for people with existing lung conditions or weakened immune systems.⁸

These cases involved poor overall hygiene, not simply using the wrong type of water. The message is that the type of water matters less than whether you are regularly dumping, rinsing, and drying your humidifier chamber. Distilled water that sits in an unwashed chamber for a week poses a greater risk than fresh tap water in a clean chamber, because the standing water gives microorganisms time to multiply regardless of whether minerals are present.

How Cleaning Habits Matter More Than Water Type

If there is a single thing to take away from the clinical literature, it is that CPAP hygiene habits dwarf the choice of water type in determining infection risk. Here is what a sensible daily and weekly routine looks like:

Daily: Empty any leftover water from the humidifier chamber each morning. Rinse the chamber with warm water and let it air-dry with the lid open. Do not leave yesterday’s water sitting in the chamber all day and then add fresh water on top of it.
Weekly: Wash the chamber, mask, and tubing in warm water with a small amount of mild dish soap. Rinse thoroughly and allow everything to dry completely before reassembling. Avoid harsh chemicals, bleach, or scented soaps, which can leave residues that irritate your airways.
Monthly or per manufacturer schedule: Inspect the chamber for mineral scale, cracks, or discoloration. Replace disposable filters on schedule. Check mask cushions for wear.

Mineral buildup from tap water use makes the weekly cleaning harder because you need to dissolve or scrub off the white crust. A soak in a mixture of one part white vinegar to three parts water for about 20 minutes usually loosens scale. If you have been using tap water regularly and notice persistent chalky deposits that won’t come off, it may be time to replace the chamber rather than fight the buildup, since rough or pitted surfaces give bacteria better places to cling.

Who Needs to Be More Careful

For a generally healthy person using CPAP for obstructive sleep apnea, the occasional night of tap water is a low-risk event. But certain groups should be more cautious about water quality and equipment cleanliness. People with chronic lung diseases like COPD or bronchiectasis are more vulnerable to opportunistic infections from waterborne bacteria.⁸ Immunocompromised individuals, including those on chemotherapy, long-term corticosteroids, or immunosuppressive drugs, face higher stakes from any microbial exposure. One case report documented hypersensitivity pneumonitis from a fungus (Cryptococcus laurentii) growing in a humidifier, affecting a patient who was not immunosuppressed, which suggests that even people with healthy immune systems can react to contaminated humidifier vapor if the exposure is repeated.⁹

If you fall into one of these higher-risk categories, sticking with distilled or sterile water and adhering to a strict cleaning schedule is worth the extra effort. Running the machine dry for a night is a better choice than using water of uncertain quality.

Seasonal and Environmental Considerations

Your need for humidification is not constant year-round. In winter, cold and dry indoor air can make CPAP without humidification especially uncomfortable, with more nasal congestion and throat dryness. Research measuring the air inside CPAP masks found that both absolute humidity and temperature were significantly lower in winter compared to summer, regardless of whether heated humidification or heated tubing was used.¹⁰ That means the benefit of humidification is greatest during cold months, and running dry in winter will likely feel worse than running dry in summer.

Conversely, in humid summer weather, you may find that you can comfortably lower your humidifier setting or skip it entirely without noticing much difference. Some users report condensation building up in their tubing during hot, humid nights, sometimes called “rainout,” which is the opposite problem. If you live in a humid climate and are debating whether to stress about distilled water, it is worth experimenting with your humidifier turned down or off during warmer months. You may discover you do not need it at all during that season.

Heated tubing, available for many modern CPAP models, helps reduce condensation by keeping the air warm all the way to the mask. It does not replace the humidifier, but it makes the humidification more efficient and can allow you to use a lower humidity setting, which means the chamber uses less water per night. Some users who switch to heated tubing find that a small amount of water lasts longer, reducing how often they need to refill with distilled.

Common Misconceptions About CPAP Water

A widespread belief is that any non-distilled water in a CPAP will immediately cause a lung infection. The evidence does not support that level of alarm. The study that tested a convection-type humidifier found that bacteria and solutes in the water were not carried into the airstream.⁴ The infections documented in case reports involve prolonged neglect of cleaning, not a one-time water substitution. The danger is stagnant, contaminated water and dirty equipment, not a single night’s use of tap water in an otherwise clean machine.

Another misconception is that distilled water is somehow “medically sterile.” Distilled water is produced by boiling water, collecting the steam, and condensing it. This process removes minerals, heavy metals, and most contaminants, but once you open the jug and pour it into your CPAP chamber, it is no longer sterile. Bacteria from your hands, the air, and the chamber itself begin colonizing the water immediately. This is why daily dumping and rinsing matters regardless of your water type. Distilled water in a dirty chamber is not clean water.

Some people also worry that breathing humidified air from a CPAP will introduce more pathogens than breathing regular room air. In reality, the air in your bedroom already contains bacteria, mold spores, and dust. CPAP machines draw in that same air and pass it through a filter before delivering it. The humidifier adds moisture, not microorganisms, provided the chamber is kept clean and the water is changed regularly. The filter at the air intake is your first line of defense, and replacing it on schedule is just as important as water choice.

What About CPAP UV Sanitizers and Ozone Cleaners

The market for CPAP cleaning gadgets has grown considerably, with devices that claim to sanitize your equipment using UV light or activated oxygen (ozone). These products are marketed as a way to skip the soap-and-water routine. The FDA has not cleared or approved any ozone or UV CPAP cleaner for use as a medical device, and in 2020 issued a safety communication warning that these devices may expose users to unsafe ozone levels. Ozone can irritate the lungs at the concentrations some of these devices produce, which is ironic for a product meant to protect respiratory health.

None of these gadgets replace the need for distilled water, either. They are designed to kill microorganisms on surfaces, not to remove mineral deposits. If you use tap water and then run an ozone cleaner, you still have mineral scale caked onto the chamber. The most reliable cleaning method remains the simplest: warm water, mild soap, a thorough rinse, and complete air-drying. It is boring, but it works, and it costs nothing beyond a minute or two of your morning.

Traveling Without Distilled Water

Travel is the most common scenario where people suddenly find themselves without distilled water. Hotels, campgrounds, and international destinations do not reliably stock it. If you are flying, check whether your CPAP machine has a travel-friendly option: some newer models have smaller, integrated humidifiers or can run without a humidifier at all by removing the chamber. Dedicated travel CPAP machines often omit the humidifier entirely to save weight and bulk.

If you want humidification while traveling, a few strategies help. Bring a small bottle of distilled water in your checked luggage (TSA and most international equivalents allow it, though liquids over 3.4 ounces must go in checked bags). Call your hotel ahead of time and ask if they can provide distilled water; some will. In many countries, pharmacies and grocery stores sell distilled water, though it may be labeled differently (“eau déminéralisée” in French-speaking countries, “agua destilada” in Spanish-speaking ones, “destilliertes Wasser” in German-speaking ones). Failing all of that, run the machine dry or use bottled water for the trip and give the chamber a thorough vinegar soak when you get home to dissolve any mineral residue.

For extended travel, some users bring a compact water distiller, though these are bulky and slow. A more practical approach for trips lasting a week or more is to buy distilled water locally on arrival and focus on daily chamber cleaning. Your lungs will not notice the difference between perfectly distilled water from your usual store and perfectly distilled water purchased in another country.