Continuous Positive Airway Pressure (CPAP) therapy remains the most common and effective treatment for obstructive sleep apnea. Many modern CPAP devices include a heated humidifier, which adds moisture to the pressurized air delivered to the user. This humidification prevents common side effects like nasal dryness, irritation, and a sore throat, significantly improving user comfort and adherence to the therapy. The water source used to fill this integrated humidifier tank is important, directly impacting the longevity of the equipment and the safety of the user. The purity of the water dictates whether the machine functions optimally or sustains damage over time.
Why Distilled Water is the Only Recommended Choice
Distilled water is created by boiling water into steam and then condensing the steam back into a liquid form. This process effectively removes nearly all dissolved solids, minerals, and impurities. Manufacturers recommend this water type because its purity prevents the accumulation of scale or residue inside the humidifier chamber. By lacking mineral content, distilled water ensures that nothing is left behind when the water evaporates into the air you breathe.
The benchmark for water quality in a CPAP humidifier is the total absence of minerals. Tap water, even if safe for drinking, contains various chemicals like chlorine and fluoride, as well as minerals such as calcium and magnesium. When these mineral-rich sources are heated and vaporized, the water molecules turn to gas, but the non-volatile mineral solids remain. Choosing distilled water avoids this buildup entirely, protecting the delicate internal components of your machine.
Assessing Bottled Water Types for CPAP Use
The term “bottled water” covers several categories, and not all are suitable for a CPAP machine. Bottled spring water and mineral water are explicitly unsuitable because they are marketed to contain naturally occurring minerals. These products are designed for human consumption, meaning they will inevitably leave behind mineral deposits when used in a heated CPAP humidifier.
Purified water, which often undergoes reverse osmosis or deionization, is generally the safest bottled option besides distilled water. While purified water has most contaminants removed, it is not guaranteed to be as pure as distilled water. Some purification methods may leave trace amounts of minerals, or the water may have been “re-mineralized” for flavor. If distilled water is unavailable, check the label for “purified” and understand this is a temporary substitute that requires more diligent cleaning of the water tank. Alkaline water is also a poor choice, as its adjusted pH is achieved through the addition of various minerals, which contribute to scale formation.
How Mineral Deposits Affect CPAP Components
The primary consequence of using non-distilled water is the formation of limescale, a hard, crusty deposit composed mainly of calcium and magnesium carbonate. As the water in the humidifier chamber heats and turns to vapor, the remaining water becomes increasingly concentrated with these dissolved solids. This residue eventually precipitates out of the solution and sticks to the surfaces of the water reservoir and the heating plate.
Scaling significantly reduces the efficiency and lifespan of the CPAP humidifier. The mineral layer acts as an insulator, preventing the heating element from properly transferring heat to the water, which reduces the moisture level in the air. Furthermore, these rough, porous mineral deposits create an ideal environment for the growth of mold and bacteria. Breathing air that passes over a contaminated water chamber can introduce these microorganisms directly into the user’s respiratory system. If the mineral buildup is severe, it can necessitate the premature replacement of the water tank or other machine components.
Guidance for Short-Term Water Use
In situations where distilled water is not available, such as during travel or a late-night shortage, alternatives can be used for a maximum of one or two nights. The most acceptable temporary option is bottled purified water due to its low mineral content compared to spring or tap water.
If neither distilled nor purified bottled water is accessible, tap water can be boiled vigorously for several minutes and then allowed to cool completely before use. Boiling tap water effectively kills most bacteria and other microbes, addressing the immediate health concern. However, boiling does not remove minerals; in fact, evaporation during boiling can slightly increase the concentration of remaining minerals. Any temporary use of non-distilled water requires immediate and thorough cleaning of the humidifier reservoir the following morning to prevent mineral residue from setting into a hard scale.