How to Avoid Water in CPAP Tubing and Masks

Table of Contents
View All
Table of Contents

A common problem faced by people who use a continuous positive airway pressure (CPAP) machine is the build-up of moisture in the mask and tube. This can cause the CPAP machine to make spitting sounds or to fill the mask with water. Both of these things can wake you up.

This article explains what causes moisture condensation in a CPAP machine—known as "rainout"—and what you can do to avoid this all-too-common problem.

Heated Tube for use with CPAP
Brandon Peters, M.D.

Causes of Rainout With CPAP Machines

The build-up of moisture in a CPAP machine is most often due to the use of a heated humidifier. This built-in feature is often recommended because non-humidified air from a CPAP machine can cause sneezing, throat irritation, dry mouth, and cracked nasal passages.

A heater humidifier is often considered a "must-have" on CPAP machines, promoting sleep and improving comfort by reducing congestion caused by nasal dryness.

However, problems can occur when heated moisture is delivered through an unheated tube. The moisture can start to condense and create tiny beads of water that run from the tube to the mask and eventually splash on your face. This is described as "rainout."

The risk of rainout increases if you sleep in a cold room, causing icy air outside of the tube to meet warm air inside of the tube. Similarly, if the humidity setting on the machine is high, moisture build-up is likely.

Signs of Water in CPAP Tube

For a CPAP machine to work at its best, you need heat and humidity in the mask and tubes to match the heat and humidity outside of the mask and tubes. Rainout can occur if you don't.

You can tell you have rainout when:

  • The CPAP machine makes spitting, popping, or gurgling noises.
  • You can feel water splashing on your face under the mask.
  • You are awakened from sleep as inhaled water causes coughing or gagging.
  • There is a lot of moisture under the mask when you remove it.
  • You can see accumulated moisture as you shake the CPAP tube.

How to Get Rid of Water in CPAP Tube

If moisture condensation has occurred, you need to get it out of the tubing so that it is completely dry and ready for the next night's use. If not, the pooled water can become a hotbed for fungus or bacteria.

There are two ways to remove water from a CPAP tube:

  • Disconnect the CPAP tube and give it a good rinse. Next, reattach the tube and run the machine for several minutes without any water in the reservoir until the tube is dry.
  • Disconnect the tube from the CPAP machine, give it a good rinse, and hang it over a doorway until it is completely dry.

You also need to give the mask, tube, and water chamber a good washing at least once weekly per the manufacturer's instructions. If you are sick, washing should be done daily.

How to Avoid Water in CPAP Tube

Rainout is common among CPAP users, but there are a few simple ways to avoid this issue and make CPAP therapy more effective.

Use Heated Tubing

Using a heated tube (also known as a climate line) is the best way to avoid condensation. A climate line delivers warm, moist air from the heated humidifier to the CPAP mask. This balances the internal and external temperature so that moisture does not condense.

Most newer CPAP units offer a climate line as a standard feature. Some models have heated wires that run the length of the tube to keep the temperature between 78 and 82 degrees F.

Older CPAP machines can be fitted with a special heated tube attachment, allowing you to keep your current machine. Hybernite Rainout Control System is among the best-known brands.

Adjust the Humidifier Setting

A simpler option is to turn down the temperature of the humidifier. Start at a lower temperature and gradually increase until you receive the highest humidity without rainout.

Though CPAP machines vary, many have humidity settings ranging from 1 to 6. Start with 3 and see how things go, increasing or decreasing as needed.

Change the Ambient Temperature

It can take trial and error to get the humidifier temperature aligned with the ambient temperature of the room.

A good place to start is to find the ambient temperature that is most comfortable for you to sleep in. You can then increase or decrease the temperature of your humidifier until you achieve the right balance.

Adjustments may be needed during hot summer months and cold winter months.

Adjust the Position of the Machine

Another useful tip is to put the CPAP machine on the floor. By doing so, the moisture that collects in the tube does not run back to your face.

While this tip may be useful in preventing splashback, it may not stop the spitting or sputtering sounds.

Wrap the Hose

You can also put the CPAP tubing under the bed covers. This will help warm the tube so that moisture is less likely to condense.

There are also special fabric covers you can buy online that slip over the tubes to help keep them warm. SnuggleHose is one of the more well-known brands. You can also make CPAP fabric covers on your own.

Summary

One common problem faced by CPAP users is the build-up of moisture in the mask and tubing. This can lead to rainout and gurgling sounds from the machine. Both of these problems are caused by the mismatch of temperature inside and outside of the CPAP tubing.

There are several ways to deal with this. This includes buying a machine with heated tubes, adjusting the temperature of the humidifier and/or bedroom, insulating the CPAP tube, or placing the CPAP unit on the floor.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American Sleep Apnea Association. The importance of CPAP humidification.

  2. Chou MSH, Ting NCH, El-Turk N, Harrington Z, Dobler CC. Treatment burden experienced by patients with obstructive sleep apnoea using continuous positive airway pressure therapy. PLoS One. 2021;16(6):e0252915. doi:10.1371/journal.pone.0252915

  3. O'Brien DT, Knowles S, Candelario DM, Robinson MR, Chowdhuri S. How to make your patient with sleep apnea a super user of positive airway pressure therapy. Fed Pract. 2016 Mar;33(3):14–22.

  4. National Council on Aging. How to clean a CPAP machine.

  5. Nilius G, Domanski U, Schroeder M, Woehrle H, Graml A, Franke KJ. Mask humidity during CPAP: influence of ambient temperature, heated humidification and heated tubing. Nat Sci Sleep. 2018;10:135-42. doi:10.2147/NSS.S158856

By Brandon Peters, MD
Brandon Peters, MD, is a board-certified neurologist and sleep medicine specialist.