All The Reasons Why A ResMed CPAP Is Leaking Water

For 30 years, CPAP therapy has been used for sleep apnea, a disorder in which breathing periodically stops during sleep. ResMed CPAP machines ensure continuous flow of oxygen via a mask during sleep, and uses water to humidify the air, which may start leaking out.

ResMed CPAP machines can start leaking water (and raining out) due to loose masks or cracks in the seal, condensation due to high temperature. Consequently, the water gathers in the mask, disturbing the user. Leaking can also occur due to separation of the tank from the metal plate.

In this article, we take you through how the ResMed CPAP machine works and explain the effects of rainout, why the CPAP machine may be leaking water and how to fix it. At the end of this article there are some additional FAQ regarding ResMed CPAPs.

Where does a ResMed CPAP leak?

A ResMed CPAP machine may leak from two primary locations.

The CPAP machine can leak water as a result of the machine’s hot, humid, and compressed air condensing in the tube, causing moisture to accumulate in the mask, and dampen the face.

This process is called ‘CPAP rainout’ and requires prompt action to keep the respiratory tract from dehydration.

It is not only uncomfortable but also impairs the adequate process of therapy.

Preventing CPAP rainout is important because dry throat and bloody nose are symptoms of sleep apnea and cause severe discomfort during sleep. The constant supply of humid air through the machine prevents dryness and aids in comfortable sleep.

A ResMed CPAP machine may also leak from the tank or machine itself, which is often only noticed as a pool of water around the machine

Plentiful Air also has a troubleshooting guide to help you if your ResMed machine is being noisy than it should be available here.

Reasons Why A ResMed CPAP Machine Is Leaking

Now that we have covered the basic construct of ResMed and what CPAP rainout means,  here are all the possible reasons why a ResMed CPAP machine may be leaking:

1. Separation of Tank From Metal Plate

One of the most common causes behind a leaking ResMed CPAP machine is the separation of the water tank from the metal plate.

The tank rests on a metal plate that heats up, eventually converting water in the tank to vapor. This moisture is then added to the air that is transported to the mask via the tube.

If the tank detaches from the metal plate, the water will not receive enough heat, and the vaporization will be inadequate.

Consequently, the water can accumulate in the mask. Although water may also leak directly from the machine because of the lack of a proper seal between the tank and plate.

To diagnose the issue, turn the device off and remove the side panel of the machine to open it. Locate the water chamber and see if it is detached from the metal plate.


Here’s how to fix the issue:

  • Remove the water tub from the machine and fill it with distilled water
  • Hold the tank at top and bottom and insert it into the side till it sits perfectly on the plate
  • Place the lid and fix it on the chamber using the four brackets
  • Put the side panel back

Look for any damage to the plate or tank that may prevent a proper seal – contact ResMed customer service for a replacement if this is the case.

2. Condensation Due To High Temperature

CPAP machines have vent holes in the mask through which the exhaled carbon dioxide is emitted. Under normal conditions, the condensation is in adequate limits and the humid air does not escape through the vent holes.

However, if the machine overheats, the high temperature tends to increase condensation, which results in leakage.

The most obvious sign of high condensation is a hissing sound during inhalation, especially in the case of full-face masks.


Reducing the temperature will help resolve the issue, to adjust it:

  • Locate the dial and highlight the thermometer icon by turning it on
  • Push the dial
  • Turn the dial again and set the new temperature

3. Loose Seal

CPAP masks are supposed to fit on the face and form a seal, preventing air from leaking (only small vents are an outlet for exhaled air). If your mask does not suit your face shape or size, the loose seal will allow the air to escape.

As a consequence of loose face masks, condensation will occur whenever the room temperature is lower than air within the mask.

If your ResMed CPAP mask does not perfectly fit the face, it is most likely the cause of rainout.


The only fix, in this case, is to replace the mask.

You can consult your respiratory therapist to help you pick the right size of CPAP mask for yourself.

4. Cracked Mask

Like a loose seal, any cracks in the mask will also break the seal, causing condensation.

The temperature and humidity of the air inside the unit are naturally higher than room temperature and RH (relative humidity), respectively, due to the built-in humidifier. This difference leads to the accumulation of vapors in the mask as condensation.

You can check for any cracks in the mask by tightening the seal.

  • Wear the mask while sitting
  • Turn the machine on
  • Lay down and tighten the seal with the help of straps
  • Inflate the outer layer by pulling the mask away from the face for a few seconds
  • Lower it down

Observe the machine for a few hours. The persistence of leakage will confirm any cracks in the mask.


Replace the old CPAP mask with a new one. Make sure to buy the mask in the appropriate type and size.

One of the primary reasons behind cracks in the mask is degradation due to dirt and oils. Regular maintenance of the unit as instructed in the user manual is the best way of preventing possible cracks and eventual leaks.

If your ResMed CPAP machine is not only leaking but creating excessive noise then read this detail troubleshooting guide on how to fix it.

How Does A ResMed CPAP Work?

To identify and troubleshoot a problem, it’s important to first know how the CPAP machine works. Three basic components make up a ResMed CPAP system: a machine, mask, and tube.


CPAP therapy delivers pressurized air to the user.

A ResMed CPAP has:

  • A motor that draws in air from the room and compresses it to increase pressure.
  • An air filter that sanitizes the air and makes it healthy to breathe.
  • A heater and a water tank that heats the air and imparts moisture to it.


The tube is essentially a pathway for air transmission to the mask from the CPAP machine.

Some ResMed tubes like AirMini Tubing, Standard Tubing (Cuffed), Mask Short Tubing Assembly, etc., also have heaters that prevent condensation in the compressed, humid air.


The hot, humid, filtered air is transferred for inhalation via a mask.

ResMed has three masks, and choosing one that is suitable for yourself is critical to ensure successful therapy. Following are the three ResMed masks:

1. Nasal Pillow Masks

Nasal pillow masks are minimal in design and specially designed for claustrophobic people. They are lightweight and rest against your nostrils.

However, they cannot generate a lot of pressure and are not good for severe sleep apnea.

2. Nasal Masks

Nasal masks cover the nose and provide higher pressure in oxygen than nasal pillow masks.

However, they are not suitable for mouth breathers unless used with a chin strap (which might feel uncomfortable).

3. Full Face Masks

As the name suggests, these masks cover the entire face and cater to mouth and nose breathers.

They are ideal for people who require higher pressure.

Why Is My ResMed CPAP Machine Running Out Of Water?

A ResMed CPAP machine typically runs out of water as a result of low external temperatures (relative to inside the hose and mask), and is a common problem in Winter. The amount of water ResMed CPAP machines use is directly proportional to the pressure and set temperature.

If the unit runs out of water too early, consider decreasing the temperature of the CPAP or invest in a ResMed capable of holding more water (ex. 380 ml ResMed AirSense 10).

Sleep apnea worsens in winters, further exacerbating dryness in the respiratory tract. To accommodate the change, the temperature in the ResMed CPAP machines increases. Eventually, the pressure and vaporization are also raised.

This causes the ResMed CPAP machine to run out of water sooner than normal.

Since it is primarily humidification that you need, try lowering the temperature in the unit by a few degrees to overcome the problem.

Ideally, a ResMed CPAP machine should operate within the temperature range of 60-80°F.

Can I Use My ResMed CPAP Without Water?

ResMed CPAP machines can operate normally without water. Remove the water tub after detaching the side panel and turn off the built-in humidifier. The unit will still compress the air, but there won’t be any humidification.

The main purpose of CPAP therapy is to deliver a continuous supply of filtered and pressurized air to keep the air tract from any possible obstructions. Humidifiers only add moisture to the air (by vaporizing water) to help people with dryness, a common symptom of sleep apnea.

If you are comfortable without extra humidification, you can use the ResMed CPAP machine without water by turning the humidifier settings off and removing the water chamber.

Why Is My ResMed CPAP Not Using Water?

If the water levels in a ResMed CPAP tank do not change, the unit is not consuming water. This occurs when the humidifier component is off, the tank and metal plate are separated, or the humidifier is not connected to the flow generator (in which case the humidifier LED does not illuminate).


Humidification is an integral part of CPAP therapy, especially for people suffering from dry respiratory tracts. Rainout (leakage) in the unit results from several causes and can impact the machine.

Since ResMed is a go-to brand for CPAP machines, this post highlights all the possible reasons behind leakage in a ResMed CPAP. If your ResMed face mask dampens the face, refer to our article and check for each problem in the list, identify the root cause and fix it accordingly.

Theresa Orr

Theresa Orr holds a PhD in Earth Science and specializes in determining past climates from rocks using geochemistry. Her passion for clean water, soil and air drives her to provide easy to understand information for everyone to read.

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