CPAP hose rainout

I have a Resmed cpap with pillow mask. I have had this machine for two years. The last 2 nights there has been water in the hose and it blows into my nose .What causes this? I do not fill it above the fill line.


What are you experiencing is CPAP hose rainout. The rainout appears when you are using a heated humidifier, and start getting water in your CPAP hose.

The main reason that can cause the water to appear in your hose is the condensation of the air. Let me explain:

  • if the air from the CPAP comes from the humidifier at a higher temperature than the surrounding room air, then the rainout occurs.

    The air blowing through your CPAP tube then can push the water that has collected in your tube, and you can be awakened by a surprising splash in your nose or mouth.

You are not the only one with this annoying phenomenon. Many persons with CPAP experience the same problem.

If the CPAP machine is placed on the level of your head, or higher, and the temperature in your room is higher than the temperature delivered by your CPAP, then the water from the hose will have no problem to enter in your mask.

So, the first step to prevent this problem is to place the cpap machine and humidifier below the level of your head, while lying in bed.

Of course, you may also need to adjust heating controls.

I have a video that can teach you how to avoid the CPAP hose rainout with an ingenious and simple method.

You also need to be cautious in case there is a build up of water in the "U" bend of the CPAP hose as it can effect the airflow and may block it.

The method from the video didn't work? Then you should buy a CPAP hose wrap, which keeps the inside of the tube slightly warmer than the temperature just outside the tube wall.

Other methods to prevent the rainout are:

  • try turning your humidity level down.

  • raise the temperature of your bedroom at night to lessen the difference between the room temperature and the humidifier—make sure that your bedroom window is closed.

  • run the air tubing beneath your blankets to keep it warm. Alternatively, you can cover the tube with a ResMed Tubing Wrap, aluminium foil or a tube sock. The goal is to keep the tube and its air warm.

Some more great pages you might like:

I hope it helps. Don't be afraid to comment back.

Remy Thierry
Founder of Sleep Apnea Guide

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Jul 06, 2011
Condensation in CPAP hose
by: Kesh


I use a CPAP machine, do not use humidifier (no water in it but keep the heater element at high) I also have a heated air tube. In spite of all these, during winter I have rain-outs. Is there any moisture trap/chemical which I could use in the humidifier tank so that I get dry air. I do not have any dry nose ao air passage problem.



Feb 07, 2012
Helpful links
by: Remy

There is an interesting video about CPAP hose rainout here: CPAP tubing condensation.

You'll find other tips for rain out prevention here.

Good luck!

May 10, 2018
Why do my throat dry up terribly
by: Anonymous

Why do my throat get very dry when I use CPAP even with the humidifier on


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