Every manufacturer of sleep apnea machines repeatedly recommends the use of distilled water! The reason? Calcium, manganese and other contaminants found in tap water will form dangerous, sandpaper like scale within your water chamber that can become a breeding ground for bacteria, mold, and yeast. All of these pathogens thrive in warm, moist environments within cpap water chambers that can seriously endanger your respiratory system.
Invented by a sleep apnea patient who was tired of running to the store to carry heavy distilled water bottles, H2O 4 CPAP insures that you "Never Use Tap Water in Your CPAP Humidifier Water Chamber."