Do You Have to Use Only Distilled Water in the CPAP Humidifier?

Tap water may cause mineralization and be risky with travel

If you use a continuous positive airway pressure (CPAP) machine to treat sleep apnea, you likely have a heated humidifier integrated into the device. Why should you use this humidifier? Do you have to use only distilled water in the CPAP machine's humidifier? Is it possible to use tap water?

What should you use when you travel? Where can distilled water be found to buy? Learn the answers to these common questions.

Benefits of a CPAP Humidifier

CPAP is much more comfortable and tolerable if you use the heated humidifier. It may reduce dry mouth and nasal congestion. That being said, local climate and personal preference will dictate how often you need it. Depending on your manufacturer, you may be able to set the temperature and level of humidity that is delivered.

When using standard tubing, there can also be a problem with condensation within the tubes (sometimes called "rainout"), which is most troublesome when the bedroom is cool. With the additional use of climate line or heated tubing, there is little risk of this happening when turning up the humidity.

By delivering more humidity, there will be less dryness—especially in the nose and sinuses—which may reduce the risks of infections, nasal congestion, inflammation, and nosebleeds.

It is probably best to turn up the humidity so that you need to refill the water reservoir nightly, or at least every few nights, to keep it from running dry.

Can You Use Tap Water With CPAP?

The safety and quality of your water supply may be the key consideration in deciding whether to use distilled water in the humidifier.

Boiling water will kill microbes, but it will not remove minerals or chemical contaminants. These minerals that make water "hard" include calcium, magnesium, iron, and others—if they are present in the water put in the humidifier's water chamber, over time scale will develop that discolors the container and could damage the machine.

Filtered water may remove some of the minerals but may not remove living organisms or other chemicals. Bottled water that has been distilled is certainly the safest option.

Most manufacturers recommend using distilled water in your CPAP.

As for whether you're required to use distilled water in the CPAP humidifier, most manufacturers do recommend the use of distilled water. According to ResMed’s product website, the use of distilled water "will maximize the life of the water tub and reduce mineral deposits."

The site also points out that it's OK to occasionally use tap water to clean the equipment. But since the water tub is typically replaced on a regular basis—perhaps every 6 months—maximizing the product life may not be a major concern. The degree of hard mineralization that is present will depend on your water supply.

What Water to Use When Traveling

If you're traveling to a part of the world where you don't trust the water supply, you should use distilled water in the humidifier. If the water is not safe for you to drink, it is probably safer to not put it in your CPAP. Using distilled water, in this case, will minimize your exposure to potentially harmful substances.

As an example, the use of tap water within Neti pots in Louisiana has led to a few reports of harmful parasite infections affecting the brain. This condition can be fatal and treatment may be ineffective. The same risk has not been demonstrated with the use of CPAP, however.

Distilled water is available to buy at many grocery stores. It differs from regular bottled or filtered water, so read the labels carefully. If traveling overseas, it may be limited to specialty stores, including the possibility of being found in a hardware store.

What to Avoid

Ultimately, you must be aware that you'll be exposing your lungs to the water placed in the humidifier, which may motivate you to clean it on a more regular basis. Moreover, you must not place any substances in the tank that would be harmful to breathe. Perfumes, cologne, or scented oils should not be placed in the water.

Exposure to fumes from bleach, alcohol, chlorine, or ammonia may damage your lungs. The use of moisturizing, antibacterial, and glycerine-based soaps is also discouraged. Water softeners and descaling agents should also not be used in the reservoir.

It is not necessary to buy a CPAP sanitizer to clean the equipment or reduce the risk of infection.

A Word From Verywell

If you question the safety or quality of your water supply, err on the side of caution and use distilled water in your CPAP humidifier. This is especially true if you are traveling in regions of the world with unsafe water supplies.

Tap water may lead to mineralization of your water tank and the potential for undesirable exposures and effects. If used infrequently, it may not have any harmful effects. Moreover, if you don't have access to safe water, you may consider trying to use the CPAP without the humidifier instead.

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  1. Quinn A, Shaman J. Health symptoms in relation to temperature, humidity, and self-reported perceptions of climate in New York City residential environmentsInt J Biometeorol. 2017;61(7):1209‐1220. doi:10.1007/s00484-016-1299-4

  2. ResMed. Setting up your humidifier.

  3. Wenzel M, Klauke M, Gessenhardt F, et al. Sterile water is unnecessary in a continuous positive airway pressure convection-type humidifier in the treatment of obstructive sleep apnea syndrome. Chest. 2005;128(4):2138-40. doi:10.1378/chest.128.4.2138

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