Continuous Positive Airway Pressure (CPAP) therapy is an effective treatment for obstructive sleep apnea, delivering pressurized air to keep airways open during sleep. Most CPAP devices include a heated humidifier to add moisture to the airflow, preventing dryness and irritation in the user’s nose, mouth, and throat. CPAP manufacturers and medical experts universally recommend filling this humidifier with distilled water. Deviating from this standard practice by using tap, filtered, or bottled water introduces risks, primarily impacting equipment lifespan and the user’s respiratory health.
Risk to CPAP Equipment: Mineral Deposits and Scaling
The primary mechanical consequence of using non-distilled water is the rapid buildup of mineral deposits, commonly known as limescale or scaling. Tap water and most bottled waters contain dissolved solids, such as calcium, magnesium, and iron. When the CPAP humidifier’s heating plate warms the water, the pure water evaporates into a gas, but these non-volatile minerals are left behind in the water chamber.
Over time, this concentration of minerals forms a crusty, white, or chalky residue on the heating element and the walls of the water chamber. This layer of scale reduces the efficiency of the humidifier, making it harder for the heating element to transfer warmth to the water. A persistent buildup can eventually cause the heating plate to overheat, potentially damaging the component or shortening the overall lifespan of the CPAP machine. Mineral deposits also create rough surfaces within the chamber, which become ideal spots for microorganisms to attach and colonize.
Direct Health Hazards: Airborne Contaminants and Microorganisms
The health risks of using non-distilled water stem from the direct inhalation of aerosolized contaminants that are otherwise safe to swallow. Unlike the digestive tract, which uses stomach acids to neutralize many microorganisms, the respiratory system has fewer defenses against inhaled pathogens. Tap water, even in areas considered safe for drinking, is not sterile and can harbor bacteria, fungi, and protozoa.
When the CPAP humidifier heats and vaporizes the water, any microorganisms present, such as Legionella spp., Pseudomonas aeruginosa, or Acanthamoeba, can become airborne and inhaled deep into the lungs. This aerosolized inhalation bypasses the body’s natural filtering mechanisms, increasing the risk of serious respiratory infections, including pneumonia-like illnesses. The mineral residue from scaling can also be inhaled as fine particulates, causing respiratory irritation or inflammation. Tap water also contains chemical additives like chlorine or fluoride, which are aerosolized and can irritate the sensitive tissues of the respiratory tract.
Examining Common Water Alternatives and Their Impurities
Many users mistakenly believe that common alternatives are sufficiently pure, but distillation is a distinct purification process. Distilled water is created by boiling water into steam and then condensing the steam back into a liquid, separating the pure water molecules from nearly all dissolved solids, minerals, and microorganisms. Water that is merely filtered, such as through a standard pitcher or refrigerator filter, only removes larger particles and some chemicals.
Filtered water, purified bottled water, and even water treated with reverse osmosis (RO) still contain trace amounts of dissolved minerals and solids. RO water, while purer than tap water, may retain enough minerals to cause scaling over time in the heated chamber. Bottled spring or mineral water is the least suitable alternative, as it is intentionally rich in minerals like calcium and magnesium, which will cause significant and rapid scale buildup. The purity level achieved by distillation is the only one that reliably prevents both mineral buildup and the aerosolization of contaminants in the CPAP humidifier.
Temporary Solutions and Necessary Cleaning Protocols
If distilled water is unavailable, a temporary alternative can be used, provided it is followed by aggressive cleaning. Use tap water that has been boiled for at least five minutes and then cooled completely before being added to the humidifier. Boiling kills most harmful bacteria and pathogens, substantially reducing the immediate health risk. However, boiling does not remove the dissolved minerals, meaning the risk of scale buildup remains high.
The use of any non-distilled water necessitates immediate and thorough cleaning protocols to mitigate damage. After using the alternative water for a single night, the water chamber should be emptied and cleaned with mild soap and warm water. If scale or a residue is visible, a weekly soak in a solution of one part distilled white vinegar to three parts distilled water for about 20 minutes can help break down the mineral deposits. The chamber must then be rinsed thoroughly with distilled water and allowed to air dry completely before the next use.