The Complete Guide to Using Distilled Water in Your CPAP Machine

If you use a CPAP machine for sleep apnea treatment, you have likely wondered about the best type of water to use in your humidifier chamber. The answer is simple: distilled water is the gold standard for CPAP therapy. This comprehensive guide explains why distilled water matters, how to use it correctly, and what happens when you make the wrong choice.

Why Your CPAP Machine Needs Distilled Water

CPAP machines with heated humidifiers require water to add moisture to the air you breathe throughout the night. This moisture prevents the dryness and irritation that can occur when breathing pressurised air for extended periods. However, not all water is suitable for this sensitive equipment.

Tap water contains minerals such as calcium, magnesium, and iron. When heated in your CPAP humidifier, these minerals remain behind as the water evaporates, creating a white or yellowish residue known as limescale or mineral buildup. Over time, this buildup can clog your humidifier chamber, reduce its effectiveness, and potentially harbour bacteria that could affect your health.

Distilled water, on the other hand, has undergone a purification process that removes virtually all minerals and impurities. When distilled water evaporates in your CPAP humidifier, it leaves no residue behind, keeping your equipment clean and functioning optimally.

The Health Implications of Water Choice

Beyond equipment maintenance, your water choice directly impacts your health. The warm, moist environment inside a CPAP humidifier chamber creates ideal conditions for bacterial and mould growth if not properly maintained. Mineral deposits from tap water provide surfaces where these microorganisms can thrive.

Breathing air that has passed over contaminated water can lead to respiratory infections, allergic reactions, and other health complications. For individuals already dealing with sleep apnea and related conditions, these additional health risks are particularly concerning. Using distilled water significantly reduces these risks by eliminating the mineral deposits where bacteria love to grow.

Medical professionals and CPAP manufacturers universally recommend distilled water for this reason. Major brands like ResMed, Philips Respironics, and Fisher & Paykel all specify distilled water in their user manuals and maintenance guidelines.

Daily CPAP Water Management Best Practices

Proper water management extends beyond simply choosing distilled water. Following these daily practices ensures optimal CPAP therapy and equipment longevity:

Each morning, empty any remaining water from your humidifier chamber. Allowing water to sit in the chamber during the day promotes bacterial growth, even when using distilled water. Rinse the chamber with fresh distilled water and allow it to air dry completely before your next use.

Fill your humidifier chamber to the maximum fill line each night before use. Overfilling can cause water to enter your CPAP tubing, potentially reaching your mask and disrupting your sleep. Underfilling may result in the humidifier running dry during the night, reducing comfort and potentially damaging the heating element.

Keep your distilled water container tightly sealed when not in use. While distilled water does not spoil in the traditional sense, exposure to air can allow airborne contaminants and dust to enter. Once opened, use your distilled water within one to two weeks for CPAP applications.

Weekly Cleaning and Maintenance

In addition to daily rinsing, your CPAP humidifier chamber requires weekly deep cleaning. Mix a solution of one part white vinegar to three parts distilled water. Soak the chamber in this solution for approximately 20 minutes, then rinse thoroughly with distilled water. Allow the chamber to dry completely before reassembling.

This vinegar solution helps dissolve any minor mineral deposits that may accumulate despite using distilled water. It also provides additional sanitisation without the harsh chemicals found in some cleaning products. Never use bleach, scented soaps, or abrasive cleaners on your CPAP equipment, as residues from these products can irritate your airways.

Replace your humidifier chamber according to manufacturer recommendations, typically every six to twelve months. Even with proper care, the plastic can degrade over time, developing small cracks where bacteria can hide.

Travelling with Your CPAP Machine

Maintaining your distilled water routine while travelling presents unique challenges. When flying domestically within Australia, you can typically bring distilled water in your checked luggage without issue. However, security restrictions may limit quantities in carry-on bags.

Many CPAP users find travel-sized distilled water bottles convenient for trips. These smaller containers, often 350ml or 500ml, are easier to pack and ensure you always have appropriate water available. Our product comparison tool can help you find travel-friendly distilled water options available in Australia.

If distilled water is unavailable at your destination, bottled water labelled as purified or spring water is a temporary alternative. However, return to distilled water as soon as possible, and clean your humidifier chamber thoroughly upon returning home to remove any mineral deposits that may have accumulated.

Common Mistakes to Avoid

Many CPAP users unknowingly compromise their therapy through simple mistakes. Using filtered water from a home pitcher filter is a common error. While these filters improve taste, they do not remove the minerals that cause problems in CPAP humidifiers.

Similarly, boiled water is not equivalent to distilled water. Boiling kills bacteria but concentrates minerals rather than removing them. Some users assume that reverse osmosis water is acceptable, but quality varies significantly between systems, and mineral content may still be problematic.

Another frequent mistake is reusing water from the previous night. Even distilled water can become contaminated after sitting in a warm humidifier chamber. Always start each night with fresh water for optimal hygiene and therapy effectiveness.

Finding Quality Distilled Water in Australia

Distilled water is readily available throughout Australia at supermarkets, pharmacies, and automotive supply stores. For CPAP use, look for products specifically labelled as distilled or steam-distilled water. Some brands market water as CPAP water, which is simply distilled water in convenient packaging.

When purchasing, check that the container is sealed and undamaged. Store distilled water in a cool, dark place away from direct sunlight. Heat and light exposure can potentially degrade plastic containers over time.

For regular CPAP users, purchasing larger containers often provides better value. A five-litre container typically lasts several weeks for most users and costs less per litre than smaller bottles. Use our free distilled water comparison tool to find the best products and prices for your needs.