Continuous Positive Airway Pressure (CPAP) therapy is a common and effective treatment for obstructive sleep apnea. Many modern CPAP machines incorporate a heated humidifier, which introduces moisture into the pressurized air stream to prevent dryness and irritation of the nasal passages and throat. Adding humidity improves user comfort, which influences how consistently a person uses the device. Manufacturers recommend using only distilled water in the humidifier tank to maintain the machine’s function and the user’s health. When the supply runs out, the immediate concern is how to continue therapy safely until a new supply can be found, requiring an understanding of the recommendation and temporary alternatives.
The Necessity of Distilled Water
Distilled water is the industry standard for CPAP humidification because it lacks dissolved solids. Water naturally contains various minerals, such as calcium and magnesium. Distillation removes these impurities by boiling the water into steam and condensing it back into a liquid state. When tap or filtered water is heated, the water evaporates, but the minerals remain in the chamber. These minerals concentrate over time, forming a hard, chalky residue known as scale on the heating plate and tub surfaces, which ultimately reduces machine efficiency.
Acceptable Short-Term Water Substitutes
If distilled water is unavailable, temporary substitutes should be used for only one or two nights to avoid interrupting sleep therapy. The most accepted temporary substitute is boiled and cooled tap water, which addresses biological risks. To prepare this water, tap water must be brought to a full, rolling boil for a minimum of five minutes. This extended boiling time kills most bacteria, viruses, and potential pathogens. The water must then be allowed to cool completely to room temperature before being added to the CPAP reservoir.
Other Temporary Options
Another temporary option is sterile water, often sold in pharmacies for use with nebulizers. Sterile water is pathogen-free, making it a safe alternative from a microbiological standpoint, though it may still contain trace minerals. Bottled spring water or purified water can also be used in a pinch, but these options carry the highest risk of scale formation. These bottled waters are often not sterile and contain minerals that will begin to leave residue after even a single night of use. Regardless of the solution chosen, discard any unused portion the following morning and thoroughly rinse the humidifier chamber.
Risks Associated with Untreated Water Use
Mechanical Risks
Ignoring the requirement for distilled water and habitually using tap or non-purified water introduces risks of mechanical failure. The most immediate consequence is the accumulation of mineral scale on the humidifier’s heating element and the inner surfaces of the water chamber. This scale acts as an insulator, forcing the heating plate to work harder and hotter to achieve the required humidity level, which ultimately shortens the operational lifespan of the component. Over time, excessive scale buildup can significantly reduce the efficiency of the humidifier, making the air feel less moist. Damage resulting from mineral deposits is often explicitly excluded from standard warranty coverage, meaning the user may be responsible for replacing the damaged humidifier base or an entire CPAP unit.
Health Risks
The health risks associated with using untreated water are concerning, as tap water is not sterile. It naturally contains microorganisms, including bacteria, fungi, and sometimes even protozoa. When this water is aerosolized by the humidifier’s heating process, these pathogens are delivered directly into the user’s upper and lower respiratory tracts. The warm, moist environment of the CPAP water chamber provides an ideal breeding ground for these organisms, leading to rapid proliferation of bacteria and mold within the device. Inhaling these contaminants can cause respiratory irritation, sinus infections, or, in rare instances, pneumonia.
Humidifier Cleaning and Long-Term Water Sourcing
Maintaining the CPAP humidifier requires consistent, preventative care to mitigate the effects of any impurities, even when using distilled water. The water chamber should be emptied and rinsed daily, regardless of how much water was used, to prevent stagnant water from becoming a breeding site for microbial growth. A thorough weekly cleaning is also necessary, typically involving washing the chamber with mild soap and warm water, followed by a complete air-dry. For a deeper cleaning or to remove minor mineral residue, a solution of one part white vinegar to four parts water can be used to soak the chamber for thirty minutes before rinsing thoroughly. To prevent future emergencies, a person should establish a reliable long-term sourcing strategy for distilled water, ensuring the therapy is never interrupted.