What is Distilled Water?
Distilled water is purified through a distillation process that involves boiling water into steam and then condensing it back into liquid form. This method effectively removes minerals, bacteria, viruses, heavy metals, and other contaminants. The result is ultra-pure water—free from impurities that could affect both health and device performance—making it the ideal choice for medical applications, including use in Continuous Positive Airway Pressure (CPAP) machines.
Benefits of Humidification with a CPAP Device
Humidification adds moisture to the air delivered by your CPAP machine, significantly reducing the risk of dryness and irritation in the nasal passages, throat, and airway. This is especially helpful for users who experience nasal congestion, sore throat, or mouth dryness during therapy.
When paired with distilled water, CPAP humidifiers provide optimal performance and hygiene. The key benefits include:
- Prevents Mineral Buildup
Tap water contains minerals such as calcium and magnesium that, over time, can form scale deposits inside the water chamber and tubing. Distilled water eliminates this risk, protecting the integrity and lifespan of your CPAP equipment. - Reduces Risk of Infections
Tap water may carry bacteria, mold spores, and microorganisms that can multiply in the warm, moist environment of a CPAP humidifier. These contaminants can be aerosolized and inhaled during therapy, increasing the risk of respiratory infections, sinusitis, and allergic reactions. Distilled water eliminates this concern due to its sterility and purity. - Improves Therapy Comfort
With consistent humidification, users experience fewer issues with dryness, congestion, or nosebleeds, leading to better adherence and overall comfort.
Risks and Side Effects of Using Tap Water in CPAP Humidifiers
Despite being readily accessible, tap water poses several health and equipment-related risks when used in CPAP devices:
- Bacterial and Fungal Contamination:
Tap water may contain Pseudomonas, Legionella, and other pathogens. Over time, these can accumulate in the humidifier chamber and be inhaled, leading to lung infections and other respiratory complications. - Mineral Scaling and Device Damage:
The minerals found in tap or even spring water can form white residue and crust in the chamber and on internal components, which may impair heating efficiency and lead to early device failure. - Allergic Reactions and Irritation:
Chemicals used to treat tap water (such as chlorine) or naturally occurring elements (like sulfur) can cause irritation or allergic responses in sensitive individuals when vaporized and inhaled. - Mold Growth in Reservoir:
Tap water, especially if left standing overnight, provides a breeding ground for mold and biofilm. These organisms thrive in the humid environment of CPAP devices and can lead to chronic respiratory issues if not properly controlled.
According to recent guidance from sleep therapy experts and the Sleep Foundation, distilled water remains the safest and most effective option for CPAP humidification, ensuring both patient safety and equipment longevity.
How Often Should You Refill the CPAP Water Chamber?
To maintain hygiene and performance, follow these best practices:
- Daily Maintenance: Empty any remaining water each morning and allow the chamber to dry completely.
- Refill Nightly: Use fresh distilled water each night before use.
- Weekly Cleaning: Clean the water chamber at least once a week using a mild detergent or a vinegar-water solution, then rinse thoroughly with distilled water.
Final Thoughts
Using distilled water in your CPAP humidifier isn’t just a recommendation—it’s a standard of care that supports optimal therapy outcomes, device protection, and respiratory health. While research such as the 2005 study in Chest suggested sterile water may not be absolutely necessary for all humidifiers, newer data and clinical practice support distilled water as the safest long-term solution for patients using CPAP at home. Contact us to learn more about your CPAP therapy, CPAP supplies, maintaining and cleaning your supplies and equipment.
Protect your health, protect your machine—use distilled water every night.
References:
Miko, S., Collier, S. A., Burns-Lynch, C. E., AndĂşjar, A. A., Benedict, K. M., Haston, J. C….Cope, J. R. (2023). (Mis)perception and Use of Unsterile Water in Home Medical Devices, PN View 360+ Survey, United States, August 2021. Emerging Infectious Diseases, 29(2), 397-401. https://doi.org/10.3201/eid2902.221205.
Wada, K. (n.d.). Say no to using tap water in home medical devices. The Ohio State University Wexner Medical Center. Retrieved January 30, 2023, from https://wexnermedical.osu.edu/blog/say-no-to-using-tap-water-in-home-medical-devices
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):2138-2140. doi:10.1378/chest.128.4.2138
Meadows, A. (2024, May 7). Should you use distilled water for a CPAP machine? Sleep Foundation. Retrieved April 14, 2025, from https://www.sleepfoundation.org/cpap/water-in-cpap