Machine and humidifier
CPAP Water in Tube or Mask (Rainout): Causes and Fixes
Water in your CPAP hose or mask is called rainout. It happens when warm, humidified air cools on its way through the tubing and the moisture condenses into droplets. Heated tubing, a slightly lower humidity setting, a warmer tube temperature and keeping the machine below the level of your bed fix it for most people.
Signs
- Water droplets on your face or in the mask cushion
- Gurgling or bubbling sound in the hose
- Visible water pooled in the low point of the tubing
- Waking up suddenly from a wet face or a splash of water
- Damp mask cushion that will not seal
Common causes
- Air cooling inside the tube
- Rainout happens when heated air cools in your tubing and reaches your mask as water. The bigger the gap between the warm humidifier and a cool bedroom, the more water drops out.
- Humidity set high for the room
- If the humidifier puts more moisture into the air than the tube can carry at its temperature, the extra condenses. The AirSense 11 user guide lists humidity set too high and tube temperature set too low as the causes of droplets on your nose, in the mask and in the tubing.
- Standard (unheated) tubing
- A standard hose has no way to keep the air warm, so it cools to room temperature along its length.
- Machine sitting higher than you
- Water that condenses runs downhill. If the machine or humidifier is above your head, droplets drain toward the mask instead of back toward the machine.
Fixes to try, easiest first
Move the machine below your mattress
Set the machine on a nightstand or shelf that is lower than the top of your mattress, so any condensation drains back toward the humidifier instead of into your mask. Philips also states the humidifier must be positioned below the mask connection and kept level.
Let the tube run in a gentle line without a deep sag where water can collect.
Turn the humidity down one step
On most machines humidity is a patient comfort setting in the menu. Lower it by one level, sleep on it for a night or two, and repeat only if water keeps appearing.
If you go too low you may trade rainout for a dry nose or mouth, so change one step at a time.
Turn the tube temperature up if you have heated tubing
With a heated tube, raising the tube temperature keeps the air warm all the way to the mask. ResMed suggests small changes, because air much warmer in the humidifier than in the tube is what causes rainout.
On the AirSense 11 you can leave Climate Control on Auto, which ResMed says protects against rainout, or set the tube temperature yourself between 16 and 30 C (about 60 to 86 F).
Use Climate Control Auto if your machine supports it
ResMed machines with a ClimateLineAir heated tube and the humidifier tub can run Climate Control Auto. It adjusts humidity and tube temperature together based on room conditions to keep moisture from condensing. Check your machine's comfort menu or user guide for the exact name on your model.
Insulate the hose
A fabric tubing cover or wrap keeps a standard hose from cooling as fast. ResMed suggests a tube wrap and notes it is especially helpful in very cold rooms. You can also run the hose under your blanket so your body heat keeps it warm.
Upgrade to heated tubing
Heated tubing is the most reliable fix. It has a heating wire that keeps the air at a set temperature until it reaches your mask. Make sure you buy the heated tube made for your exact machine model, since connectors are not interchangeable between brands.
Warm the bedroom slightly
Rainout gets worse as the room gets colder. Raising the room temperature a few degrees narrows the gap between the humidifier and the room air.
Empty and dry the tube in the morning
Hang the hose to drain and air dry each day so leftover water does not sit in it. This also keeps the tube clean.
Rainout itself is a comfort problem, not a medical one, and you can fix it with comfort settings and equipment. Call your equipment provider if you cannot find a humidity and tube setting that stops both rainout and dryness, or if water is getting into the machine itself. If you are waking often, pulling the mask off, or skipping therapy because of water in the mask, tell your sleep doctor, because missed hours mean untreated apneas.
Supplies that can help
Tubing with a built-in heating wire that keeps humidified air warm all the way to the mask, which is the main fix for rainout (water droplets …
A fabric sleeve that slips over CPAP tubing to insulate it, reduce condensation and make the hose feel softer against your skin.
A simple hook or hanger for drying CPAP tubing vertically after washing, and for keeping it off the floor.
Distilled water is what most CPAP humidifier chambers are meant to be filled with, because it leaves little or no mineral scale behind.
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Mask types this applies to
Frequently asked questions
Is rainout dangerous?
Rainout is uncomfortable but the water itself is condensed from the humidifier, so it is not harmful in small amounts. The real risk is that it wakes you up or makes you take the mask off, which cuts your therapy hours. Keep the tubing and water chamber clean so the moisture is not sitting in a dirty hose.
Why do I only get water in my CPAP hose in winter?
Cold bedroom air cools the tube faster, so more of the moisture condenses before it reaches your mask. That is why many people need a lower humidity, a higher tube temperature or a tubing cover in colder months.
Should I turn off the humidifier to stop rainout?
You can, but many people then wake up with a dry mouth or nose. Try lowering humidity one step, raising tube temperature, and moving the machine below the bed first. Turning humidity off is a last resort.
Does heated tubing really stop rainout?
Heated tubing keeps the air warm along the whole hose, which is the root cause ResMed identifies. Paired with an automatic setting like Climate Control on supported machines, it prevents rainout for most users.
Sources
Last reviewed October 11, 2026. How we research · Report an error