Machine and humidifier
CPAP Humidifier Water Runs Out Before Morning
If your water chamber is empty by morning, the most common reasons are mask leak, high humidity or tube temperature settings, a very dry or cold room, or not filling to the maximum line. ResMed says a humidifier should not normally run out of water and that an empty tub often points to mask leak.
Signs
- Empty or nearly empty water chamber when you wake
- Dry mouth or nose late in the night
- Machine message about the humidifier
- Water use that suddenly increased compared with before
Common causes
- Mask leak
- Air escaping around the mask pulls more air through the humidifier. Both ResMed and Philips name mask leak as a reason the tank empties early.
- Chamber not filled to the max line
- Philips says a tank filled to the maximum fill line should last a typical sleep session under most conditions.
- High humidity or heated tube settings
- Higher settings evaporate more water.
- Dry or cold room
- Philips lists very dry or cool room conditions as a factor, and ResMed says cold conditions can magnify an existing leak.
- Long sleep session
- More hours means more water used.
Fixes to try, easiest first
Fill to the maximum line every night
Remove the chamber and fill it to the max line with fresh water before bed. Fisher and Paykel recommend filling it away from the machine, over a sink, so water does not spill into the device.
Check and fix mask leak
Refit your mask while lying in your sleep position with the air on. Check your machine or app for a leak reading. If you use a nasal mask and breathe through your mouth, mouth leak can also drain the tank.
Lower humidity one step
If you are not dry at night, lower the humidity one level and see whether the tank lasts.
Use a room humidifier in very dry air
In very dry rooms, ResMed suggests asking your provider whether a room humidifier would help.
Check the chamber for leaks
Look for cracks or water on the table under the machine. A leaking chamber empties itself.
Call your equipment provider for a replacement chamber or a refit if leak stays high. Tell your doctor if your data shows large leak night after night or you are waking dry and tired, since leak can reduce how well CPAP treats your apnea.
Supplies that can help
Distilled water is what most CPAP humidifier chambers are meant to be filled with, because it leaves little or no mineral scale behind.
The removable water tank of a CPAP humidifier; it wears and needs replacing, especially if it cracks, clouds or leaks.
A soft strap that supports the jaw to help keep the mouth closed, used mainly with nasal and nasal pillow masks to reduce mouth leaks.
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Mask types this applies to
Frequently asked questions
Is it bad if my CPAP runs out of water?
The machine keeps running, but the air becomes dry and you may wake with dryness. More importantly, an empty tank is often a sign of mask leak, which can affect therapy.
Can I add more water in the middle of the night?
You can, but let the heater plate cool before you remove the chamber. Philips advises about 15 minutes of cooling to avoid burns, and fill it away from the machine.
Why does my water run out faster in winter?
Cold, dry air increases water use and can make an existing leak worse. Check mask fit first, then adjust humidity.
Sources
Last reviewed October 11, 2026. How we research · Report an error