A Continuous Positive Airway Pressure (CPAP) machine treats sleep apnea by delivering pressurized air through a mask. Most CPAP machines include an integrated humidifier, which warms and moistens the air to prevent dryness and irritation in the user’s airways. This humidification is important for comfort and compliance, but it requires the device to use water nightly. The type of water introduced into the humidifier reservoir is critical for both the machine’s function and the user’s respiratory health.
The Risks of Using Tap or Spring Water
Spring water should not be used in a CPAP machine because it contains dissolved minerals, similar to tap water. These include elements like calcium, magnesium, and other total dissolved solids (TDS). When the humidifier’s heating plate warms the water, the pure water evaporates, but the non-evaporating mineral content is left behind and becomes concentrated in the reservoir.
This concentration causes limescale, a crusty deposit that accumulates on the heating element and water chamber walls. This mineral buildup, known as scaling, impairs the humidifier’s efficiency and can damage the heating plate. Severe scaling may also create a white powder or dust that is carried into the tubing and mask, potentially irritating the user’s airways.
Beyond the mechanical risks, untreated water sources like spring water may contain microbes, including bacteria or fungi. While drinking water is generally safe, these microorganisms can be aerosolized by the CPAP humidifier and inhaled, posing a risk of respiratory infection. Warm, stagnant water left in the reservoir allows these contaminants to multiply, compounding the hygiene risk.
Why Distilled Water is the Required Standard
Distilled water is the industry standard because it is produced through a specific purification process. Water is boiled into steam, which is then condensed back into liquid, leaving behind nearly all impurities, minerals, and contaminants. This process results in a product with an extremely low level of total dissolved solids (TDS), often less than one part per million.
The near-total absence of minerals in distilled water prevents scaling and white dust formation. When distilled water evaporates, virtually no residue is left behind to foul the heating element or coat the interior of the water chamber. This purity protects the CPAP machine’s delicate components, maintaining proper function and extending the humidifier’s lifespan.
Some bottled water is labeled as purified or filtered, but these processes often fail to remove the high concentration of minerals that distillation achieves. Purified or filtered water is not an acceptable long-term substitute, as remaining minerals can still cause buildup. Manufacturers recommend distillation to ensure the highest purity necessary for continuous, heated use inside the CPAP system.
Humidifier Maintenance and Hygiene
Proper cleaning of the humidifier reservoir is necessary to ensure a hygienic environment, even when using distilled water. The water chamber should be emptied of any unused water every morning to prevent microbial growth in stagnant moisture. After emptying, the reservoir should be rinsed with clean water and allowed to air dry completely, away from direct sunlight.
A thorough weekly cleaning is recommended to remove any accumulated mineral residue or biological film. The chamber should be washed by hand in warm water using a mild dish soap or a pure liquid soap. Avoid harsh chemicals, alcohol-based solutions, or antibacterial soaps, as they can damage the plastic materials.
For deep disinfection, the humidifier tub can be soaked for 30 minutes in a solution of one part white distilled vinegar to three parts water. After soaking, rinse the chamber thoroughly with clean water to remove any vinegar odor or residue. Allowing all components to air dry completely before reassembly prevents moisture from creating a breeding ground for pathogens.