Continuous Positive Airway Pressure (CPAP) therapy is a widely used treatment for obstructive sleep apnea, delivering pressurized air to keep airways open during sleep. Many CPAP users rely on a heated humidifier to add moisture to this airflow, which greatly improves comfort and helps prevent common side effects like dry mouth and nasal irritation. This humidification process is a simple but powerful way to encourage consistent use of the machine, which is directly tied to the success of the therapy. A common point of confusion for new users involves the type of water that should be used in the humidifier reservoir, with many wondering if bottled or specialty products like alkaline water are safe options. The specific question of whether alkaline water is appropriate for a CPAP machine requires an understanding of water chemistry and its effect on medical equipment.
Why Alkaline Water is Unsuitable for CPAP Use
Alkaline water is not recommended for CPAP use. Alkaline water is defined by its higher pH level, typically above 7, but its unsuitability is tied more directly to its impurity for mechanical application.
This type of water often contains elevated levels of total dissolved solids (TDS), which are the mineral salts and compounds dissolved in the liquid. Alkaline water often contains elevated levels of minerals like calcium, magnesium, and potassium, which contribute to the higher pH.
When the CPAP machine’s humidifier plate heats the water, the pure water molecules turn into vapor. This evaporation leaves behind all the non-volatile dissolved solids in the reservoir, concentrating them with each night of use.
The high concentration of TDS in alkaline water accelerates this mineral deposit process compared to standard tap water. While alkaline water may be safe for drinking, its chemical composition makes it impure for use in any device that relies on a heating and evaporation cycle.
The Recommended Water Source for Humidification
CPAP manufacturers consistently recommend distilled water for long-term use in the humidifier. Distilled water is the industry standard precisely because it is nearly devoid of the dissolved solids found in all other water sources.
The distillation process involves boiling the water into steam and then condensing the steam back into a liquid state. This method ensures that virtually all minerals, salts, and other contaminants are left behind.
The resulting water is chemically pure, containing only water molecules, with a Total Dissolved Solids (TDS) measurement near zero. Using this pure water ensures that when it is heated and vaporized in the CPAP chamber, nothing is left behind to accumulate on the equipment surfaces.
While some users may consider alternatives, such as purified or deionized water, distilled water remains the gold standard for maintaining equipment integrity. Purified water, while treated, may still contain trace amounts of minerals depending on the specific filtration method used. Choosing distilled water eliminates the chemical risk entirely, ensuring the most consistent performance for the humidification system.
Practical Impact of Mineral Deposits on CPAP Equipment
The primary consequence of using alkaline, tap, or any water high in TDS is the formation of scale, commonly known as limescale, on the humidifier’s components. This scale is a hard, chalky buildup, primarily composed of calcium and magnesium carbonate, which adheres tightly to the plastic reservoir and the metal heating plate.
The presence of this scale directly impacts the machine’s performance by acting as an insulator on the heating element. A layer of scale reduces the efficiency of heat transfer from the plate to the water, forcing the machine to work harder.
This limits its ability to achieve the desired humidity level, causing the very dryness the user was trying to prevent. Over time, this accumulation can shorten the lifespan of the humidifier and may even void the manufacturer’s warranty if the damage is directly attributable to improper water use.
Although mineral deposits can be removed with an acidic solution like diluted white vinegar, this necessary maintenance is time-consuming and often cannot fully restore the chamber’s original clarity and efficiency. Consistent use of distilled water is the only way to prevent this damaging scale formation.