Using standard drinking water in a Continuous Positive Airway Pressure (CPAP) machine with a humidifier is not recommended. While tap water is safe to drink, its composition is unsuitable for the specialized function of a CPAP humidifier, posing risks to both the equipment and the user’s health. The process of heating and aerosolizing water for inhalation alters the safety profile of common drinking water. Manufacturers advise against using unfiltered tap water to maintain machine longevity and ensure clean air delivery.
Why Tap Water Causes Damage
The risk of using tap water stems from dissolved minerals, a characteristic of water hardness. Tap water contains inorganic compounds, such as calcium, magnesium, and lime, that are left behind when the water is heated and evaporates in the CPAP humidifier’s chamber. This process concentrates the minerals, leading to the formation of hard, crusty deposits known as scale.
This mineral buildup adheres to the humidifier plate and reservoir. Over time, the scale acts as an insulator, significantly reducing the efficiency of the heating element and the humidifier’s ability to add moisture. If scaling progresses, it can clog internal components or cause the machine to malfunction entirely, potentially requiring costly replacement of the water chamber or the CPAP unit itself.
The Required Water Type
The recommended water type for CPAP humidifiers is distilled water. Distillation is a purification method where water is boiled into steam, and the resulting vapor is then condensed back into liquid form. This physical process effectively leaves all non-water substances behind, including minerals, chemicals, and microorganisms.
The resulting product has zero mineral content, which is essential for CPAP operation as it eliminates the risk of scale buildup. This pure water prevents equipment damage and ensures the humidifier performs optimally. Distilled water is distinctly different from purified, filtered, or spring water, which still retain trace minerals that cause scaling in the heated chamber.
Addressing Contaminant Exposure
Beyond the mechanical damage, using tap water introduces a significant risk of user health issues due to contamination. While stomach acids can neutralize microorganisms ingested through drinking water, the respiratory system lacks this defense mechanism. When tap water is heated in the CPAP chamber, any microbes present become aerosolized and are delivered directly into the user’s airways and deep into the lungs.
Tap water is categorized as “unsterile water” and can harbor pathogens like Pseudomonas aeruginosa, Legionella spp., and nontuberculous mycobacteria. The warm, moist environment of the humidifier chamber provides an ideal breeding ground, potentially creating a biofilm that increases the risk of respiratory infection. Tap water also contains trace chemicals like chlorine or fluoride, which are safe to drink but become irritants when inhaled as concentrated vapor. Exposure to these aerosolized contaminants can lead to respiratory irritation or pneumonia-like symptoms.
Short-Term Alternatives
In a situation where distilled water is temporarily unavailable, such as during travel, a short-term alternative may be necessary, but it is not a long-term solution. Purified bottled water or filtered tap water can be used for a maximum of one or two nights. This is because these types of water have fewer impurities than standard tap water, but they still contain trace minerals that will begin to leave deposits in the chamber.
If an alternative is used, the humidifier chamber must be cleaned thoroughly the next morning to remove initial mineral residue and prevent microorganism growth. Boiling tap water is sometimes suggested to kill biological contaminants, but this process only concentrates the mineral content as the water evaporates. Boiled tap water is a poor choice for the CPAP machine, as it accelerates mineral scaling. Return to distilled water as soon as possible to protect the machine’s function and the user’s respiratory health.