What is CPAP Rainout and How Can it be Prevented?

Have you ever woken up to water in your mask?
Ever noticed a lot of condensation in your tubing?
Has water in your hose ever stopped you from using your CPAP?

This is known as CPAP rainout. What is rainout? And why does it happen?

What’s the big deal with moisture in the air?

The normal function of the upper airway is to heat, humidify and filter the air that you breathe into your lungs.

If you have been diagnosed with sleep apnea and are using CPAP (continuous positive airway pressure), the device is blowing air into your airway all night long and you may have some leak of air through your mouth or mask (learn more about how CPAP works here or click the image below).

This can cause dry airways and inflammation.

Studies show up to 70% of CPAP users experience nasal congestion, dry nose and throat, sore throat, nose bleeds (epitaxis) or discomfort from the cold airflow CPAP (read more about the benefits of heated humidification here).

Heated humidification can reduce airway dryness and increase compliance.

What causes rain out?

If, like most CPAP users, you’re using a heated humidifier, the air is heated in the humidifier and flows through the tubing up to the mask and into your airway. As the air travels through your tubing, its temperature drops rapidly.

As the air cools, the moisture from the air condenses into droplets inside of the tubing.

The tubing can fill with water.

The water can flow down the tubing and into your mask.

This is condensation of the humidified air and is often known as “rainout.”

Solutions for CPAP rainout:

1. Move your CPAP machine

Move your CPAP machine to a lower level than your mask. Use gravity to your advantage so that the condensation does not flow to your mask.

If your CPAP is on a bedside table and the tubing drains down to your mask, try moving your machine onto a lower surface so the tubing and air flows up. If water droplets do form, they will flow back down to your humidifier and not into your mask.

2. Try wrapping your hose to keep the air warm

Wrapping the hose using specially designed tubing wrappers can help to insulate the blowing air from the lower temperature of the room, reducing “rainout.”
You can even run the tubing beneath your blankets to keep it warm.

3. Adjust the temperature in your bedroom

It’s the difference between the temperature in your bedroom and the temperature of the air in your tubing that causes the rainout. If your room is really cold at night, you’re more likely to see condensation in your tubing.

4. Adjust your humidifier settings

Talk to your equipment provider about changing your humidifier settings. If you live in a warm or very humid climate, you may not need a high temperature setting. The humidifier is trying to warm the air to around 80 degrees Fahrenheit.  

5. Use heated CPAP tubing

Heated tubing reduces rainout by keeping the temperature of the air constant as it travels from the humidifier to your mask. If the air stays warm, it doesn’t condense into droplets.

Heated tubing is designed to manage humidification in real-time based on changes in the climate in your bedroom, such as increases or decreases in temperature or humidity, and changes in your CPAP pressure and mask leak.

Check out ClimateLine heated tubing here (it is covered by most insurance-learn more about insurance coverage for supplies here).

Have you experienced CPAP rainout and think you may benefit from heated CPAP tubing?

Order ClimateLine Tubing


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  1. Tim Birdwell Reply

    I have been experiencing rain out since I’ve started this treatment in December 2018. I have the heated tube, and use to keep everything on auto. Then I started using manual , but don’t know what settings to run it on. Still getting Rail out. My cpap does sit on my night stand, which is head level , but I have the tube ran over top of my head board and I still get rain out. Maybe I need to put it on the floor, keep the hose going up over head board, and put settings back on auto.

  2. Dave Reply

    I have had “rainout” at times with my cpap machine. The noise of the water in the tube has caused me to wake a few times. What found that has helped is that I cut up an old t-shirt and rapped the tube using paper medical tape about every 6 inches to insulate the tube. It’s free and only takes a couple of minutes, and beat paying $25+ for a cover.

  3. Laura Brunetti Reply

    Thank you Dave

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