Continuous Positive Airway Pressure (CPAP) machines treat sleep apnea by delivering pressurized air through a mask. Many devices include a heated humidifier, which introduces moisture to the air stream. This humidification prevents common side effects like nasal dryness, irritation, and sore throat, making the therapy more comfortable. The humidifier requires a water source, and the quality of this water is a major concern for both machine longevity and user health.
Sterile and Distilled Water Defined
The terms “sterile” and “distilled” refer to two distinct purification processes that target different types of contaminants in water. Sterile water is defined by its lack of living microorganisms, such as bacteria, fungi, and viruses, typically achieved through boiling or autoclaving. This process ensures biological purity, but it does not remove dissolved mineral solids. Distilled water is produced by boiling water into steam and then condensing the steam back into a liquid. This physical process effectively leaves all non-volatile impurities behind, including minerals and chemicals. While sterile water is safe to use, distilled water is considered the gold standard because it specifically addresses microbial contamination and mineral buildup.
Why Water Quality is Critical for Machine and User Health
Using water that contains mineral solids, such as standard tap or spring water, poses a direct threat to the CPAP machine’s heated components. When this water is heated and converted into vapor, the dissolved minerals—like calcium, magnesium, and iron—do not evaporate. Instead, they are left behind in the humidifier chamber, where they accumulate as scale or white crusty deposits. This mineral scaling coats the heating plate and the interior of the water chamber, reducing the machine’s heating efficiency and shortening the lifespan of the unit. The buildup acts as an insulator, forcing the machine to work harder to achieve the set humidity level.
Using non-distilled water also introduces the risk of microbial contamination, which affects the user’s health. Tap water, even if safe for drinking, contains trace amounts of bacteria, mold spores, and other pathogens. Unlike the digestive system, the respiratory tract lacks a robust defense mechanism. When these pathogens are aerosolized by the humidifier and inhaled directly into the airways, they can lead to respiratory irritation or infections. Mineral deposits can also create surfaces where bacteria and fungi may adhere and multiply, increasing the biological risk over time.
Emergency Water Alternatives and Usage Guidelines
Distilled water is always the recommended choice, but temporary shortages may require alternatives. In these short-term circumstances, the safest option is to use boiled and cooled tap water. Boiling tap water vigorously for at least one minute kills nearly all microorganisms, addressing the immediate health risk. Since boiling does not remove minerals, this water must only be used temporarily for a night or two, as it will still lead to mineral residue. If bottled water is the only option, look for a label that states “purified” or “reverse osmosis” water, which generally has fewer minerals than spring water.
Regardless of the water type used, diligent daily maintenance is necessary to mitigate risks. The humidifier chamber must be emptied and rinsed every morning, as leaving standing water allows for microbial growth and biofilm formation. Only fresh, clean water should be added before each night’s therapy session. Returning to the use of distilled water should be a priority as soon as it becomes available to protect both the user’s health and the integrity of the CPAP equipment.