Comfort
Distilled water for CPAP humidifiers
Distilled water is what most CPAP humidifier chambers are meant to be filled with, because it leaves little or no mineral scale behind.
Why it helps
Tap water carries dissolved minerals that are left behind as white scale when the humidifier heats it. That scale clouds the chamber, can pit the hot plate contact surface over time, and makes cleaning harder. Distilled water avoids most of that. Some manufacturers are explicit about it: the ResMed AirSense 11 guide says its HumidAir 11 Standard tub must be filled with distilled water only, and lists distilled water as the recommended water for that tub.
How to choose
Buy plain distilled water in sealed jugs. Spring water, mineral water, and flavored or 'enhanced' water are not substitutes, because they contain the minerals you are trying to avoid. Check your own manual for which water your chamber takes. On the AirSense 11, the HumidAir 11 Standard tub (white thumb grip) takes distilled water only, while the HumidAir 11 Cleanable tub (grey thumb grip) is rated for drinking quality (potable) water. Fill only to the maximum line marked on the chamber. The AirSense 11 tub holds 380 mL, which ResMed rates for more than 8 hours between refills under its test conditions.
Empty leftover water each morning rather than topping it up, and let the chamber air dry, as your manual describes. If you see white powder deposits anyway, ResMed suggests a solution of 1 part household vinegar to 9 parts water, followed by a rinse with clean water.
Frequently asked questions
Can I use tap water in my CPAP humidifier?
It depends on your chamber. ResMed's AirSense 11 guide says the HumidAir 11 Standard tub takes distilled water only, while the HumidAir 11 Cleanable tub can use drinking quality water. Tap water in a chamber meant for distilled water leaves mineral scale, so check your manual before you switch.
Is bottled spring water the same as distilled water?
No. Spring and mineral water contain dissolved minerals, which is exactly what leaves white scale in a heated humidifier. Look for a label that says distilled.
What do I do if I run out of distilled water while traveling?
Follow your manual: some chambers allow drinking quality water and some do not. If your chamber is rated for distilled water only, using another water for a night mainly risks extra scale, which you can clean off with the 1 part vinegar to 9 parts water rinse ResMed describes.
Sources
Last reviewed October 11, 2026. How we research · Report an error