Continuous Positive Airway Pressure (CPAP) therapy uses a machine to deliver pressurized air, keeping the user’s airway open during sleep. Many CPAP devices include a heated humidifier to add moisture to the airflow, preventing dryness and irritation. The quality of the water used is a significant factor in maintaining both the equipment and the therapy’s effectiveness. Water safe to drink is not necessarily safe to aerosolize and inhale, which is why manufacturers provide specific guidance.
Why Distilled Water Is the Standard Requirement
CPAP manufacturers almost universally require the use of distilled water because it is nearly free of minerals and dissolved solids. The distillation process involves boiling water and condensing the resulting steam back into a liquid, leaving behind almost all impurities, including inorganic compounds like calcium and magnesium. This purity is the reason distilled water is the ideal choice for CPAP humidifiers.
When non-distilled water is heated in the humidifier chamber, the water evaporates into the air, but the mineral content is left behind. Over time, these residual minerals accumulate on the heating plate and the inside of the chamber, forming a hard residue known as mineral scaling or limescale. This buildup can affect the efficiency of the heating element, reducing the machine’s ability to provide adequate humidification.
Preventing this mineral accumulation is a primary reason for the strict recommendation, as scaling can significantly shorten the lifespan of the humidifier and its components. Regular use of mineral-containing water eventually necessitates the replacement of the water tub, which is an avoidable maintenance cost. By using distilled water, users ensure their equipment operates at peak performance.
The Short-Term Use of Purified Water
The question of using purified water for a single night arises when distilled water is unavailable. Purified water, typically produced using methods like reverse osmosis or deionization, is safe to drink because most contaminants and chemicals are removed. Unlike distilled water, purified water may still contain trace amounts of dissolved solids or minerals, as it has not undergone the full demineralization process of distillation.
From a health perspective, using bottled purified water for a single night is generally considered a safe, temporary substitute, as it is free of the microbes found in tap water. A single 8-hour period is highly unlikely to cause immediate harm to the machine’s components. The trace minerals present will not instantly create a performance-inhibiting layer of scale.
This temporary use should not become a regular habit, as repeated use of purified water will eventually lead to mineral buildup, just at a slower rate than with tap water. If purified water is used, it is advisable to empty the chamber completely in the morning and switch back to distilled water as soon as possible. For one night, the slight risk to the machine is outweighed by the benefit of maintaining therapy, but it is not the long-term solution.
Immediate Risks of Using Tap or Spring Water
In contrast to purified water, using standard tap water or bottled spring water carries both equipment and health risks. Tap water contains varying levels of minerals, such as calcium and magnesium, which rapidly create limescale buildup in the humidifier chamber. Spring water is naturally rich in minerals, making it an even worse choice for the machine’s longevity.
A more serious concern is the health risk posed by aerosolizing unsterile water. Tap water is not sterile and can contain bacteria, fungi, and protozoa. When the CPAP humidifier heats and evaporates this water, these microbes and chemical additives like chlorine and fluoride can be aerosolized and inhaled directly into the respiratory system.
The respiratory tract lacks the strong defenses of the digestive system, making it vulnerable to waterborne pathogens such as Pseudomonas bacteria. The use of tap water has been linked to respiratory infections in rare cases, making it the least recommended temporary alternative. If a CPAP user must choose an alternative for a single night, the immediate health risks associated with tap water make purified water the safer choice.