Waking up to a gurgling noise or water splashing on your face is the worst way to start the morning.
Key Takeaways: How to Fix It Fast
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It is condensation, not a leak. Rainout happens when warm, humid air from your machine hits the cold plastic of your hose and turns back into water droplets.
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Warm up the hose first. The most reliable fix is using heated tubing to keep the air temperature consistent all the way to your mask.
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Lower humidity in small steps. If the air is holding too much moisture for your room temperature, dial back your humidity setting by one level at a time.
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Insulate against the cold. If your bedroom is chilly and you use a standard hose, add a hose cover to block the temperature drop that causes condensation.
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Check your hose routing. Keep the machine lower than your head and avoid letting the tube dip onto the floor, where water can pool and block airflow.
Source: ResMed (heated tubing/rainout guidance)
What CPAP Rainout Is (and Why It Happens)
Definition: CPAP rainout is condensation that forms water in the hose or mask instead of keeping it as breathable vapor. It happens when warm, humid air from your machine travels through a colder tube and cools down before reaching you, turning back into liquid. A study on treatment burden in OSA highlights this as a frequent cause of awakenings, often forcing users to stop therapy just to wipe down wet gear.
Rainout matters because it physically interrupts the sleep you are trying to fix. Instead of resting, you end up dealing with loud popping noises, a damp cushion that slides around, or a sudden splash of water in your nose. It creates immediate discomfort, making it frustratingly hard to fall back asleep.
It is much more common when there is a temperature clash between your machine and your environment. You will see this most often if you sleep in a cool room, use a high-humidity setting for comfort, or use standard tubing without insulation. The physics are simple: warm air cannot hold its moisture if it cools down on the way to your face.
Common signs you are having a rainout:
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Loud gurgling or bubbling noise in the tube
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Visible water droplets are collecting inside the mask
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A sudden splash of water when you roll over
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Waking up with a wet face or a damp pillow
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Water is pooling in the low point of the hose on the floor
Quick Fix Table: What to Change Based on What You’re Seeing
This table helps you identify exactly what is happening and choose the first change tonight to stop the disruption.
|
What you notice |
Most likely cause |
First change tonight |
If it still happens |
|
Water in the mask / wet cushion |
Warm humid air cools in the hose → condensation |
Increase tube temperature (if your machine supports it) |
Lower the humidity one step and re-check the next night |
|
Gurgling/bubbling in the hose |
Water is pooling in a low dip |
Drain the hose and reroute it using a hose lift or holder so it doesn’t sag |
Add a hose cover to slow heat loss in a cool room |
|
Water is collecting in the hose |
Hose is cooling too fast overnight |
Use heated tubing like the ClimateLineAir 11 or ClimateLineAir 10 |
Add a hose cover and keep the hose from touching cold surfaces |
|
The room is cold at night |
A bigger temperature drop along the tubing |
Keep the hose warmer (under the blanket or away from cold airflow) |
Slightly raise the room temperature or switch to heated tubing (see AirSense 11 PDF or AirSense 10 PDF) |
|
Air feels too wet / heavy |
Humidity is high for your room conditions |
Lower humidity one step |
Raise the tube temperature instead of lowering the humidity further |
AirSense 11 & AirCurve 11 ClimateLineAir Heated Tube
ResMed AirSense 11 AutoSet CPAP Machine
ResMed AirCurve 11 VAuto with HumidAir
ResMed ClimateLineAir Heated Tube for Airsense 10 and Aircurve 10 CPAP Machine
ResMed AirSense 10 AutoSet CPAP Machine with HumidAir Heated Humidifier
ResMed AirCurve 10 VAuto BiPAP Machine with HumidAir Heated Humidifier
Why Rainout Happens (Condensation in the Hose)
Your CPAP humidifier adds moisture to the airflow to prevent dryness. This means the air leaving your machine is much warmer and wetter than the air in your bedroom.
Problems start when that warm air enters the hose. In a cool bedroom or when the tubing is lying on top of the covers, the plastic hose cools rapidly.
As the air travels through this cold tube, it loses its heat. When humid air cools down, it loses its ability to hold moisture. The vapor condenses on the inner walls and turns back into liquid water droplets.
Finally, the continuous airflow pushes these droplets along the tube. They eventually collect in low spots to create that annoying gurgling sound or get pushed all the way to your mask, resulting in a splash on your face.
Step-by-Step Fixes for Rainout
Start by keeping the hose warm, then fine-tune your humidity settings. This order helps you solve the problem without drying out your nose and throat.
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Confirm heated tubing is on (if available): Make sure your heated tubing is plugged in correctly and enabled in your machine's comfort settings. You should notice fewer water droplets and significantly less gurgling within 1 - 2 nights.
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Increase the tube temperature first: Raise your tube temperature setting in small increments before you adjust the humidity level. The hose will feel slightly warmer to the touch, preventing the air inside from cooling down enough to condense.
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Lower humidity one step only if moisture continues: If the air feels heavy or rainout persists, reduce your humidity setting by just one level. This delivers less "wet" airflow to the tube without causing you to wake up with a dry mouth.
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Add insulation if the room is cool: Wrap a standard hose in a hose cover or tuck the tubing under your blanket to shield it from the cold bedroom air. This eliminates cold spots, resulting in fewer nights where rainout returns unexpectedly.
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Fix hose routing to remove low dips: Route your tubing so it flows downhill or stays level, ensuring there are no sagging loops where water can pool. The annoying gurgling noise usually stops immediately once the water has nowhere to collect.
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Adjust the room environment if needed: Keep your equipment away from direct drafts like fans or windows, or try slightly raising the bedroom temperature. You will find that rainout becomes much less frequent, allowing you to maintain higher humidity settings comfortably.
Common Mistakes (and why rainout keeps coming back)
Rainout usually keeps coming back when you change the humidity without addressing how cold the hose gets.
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Turning the humidity up too high in a cold room. This creates a greater temperature difference that instantly turns moisture into droplets. Raise your tube temperature or switch to heated tubing before you increase the humidity level.
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Lowering the humidity too much to "solve" rainout. This causes dryness to return, prompting you to raise the humidity back up, and the cycle repeats. Make small changes in humidity and rely on insulation or temperature controls to stop the water.
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Leaving the hose exposed to cold air from fans or windows. The tubing cools down much faster in a draft, causing condensation to form even at moderate humidity settings. Move the hose away from cold airflow or add a hose cover to shield it.
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Letting the hose sag and trap water in a low dip. Gravity traps water in low spots, creating loud gurgling noises before the air pushes it into your mask. Reroute the hose to remove sagging loops or use a hose lift to keep the line suspended.
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Ignoring leftover water after cleaning. Starting the night with moisture already inside the hose gives condensation a head start. Hang your tubing up early enough to let it dry completely before bedtime.
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Changing multiple settings at once. This makes it impossible to know which fix actually worked and often leads to frustrating over-corrections. Adjust one variable at a time to track which solution solves the problem.
Practical Optimization (comfort, setup, maintenance)
A stable setup usually comes down to combining moderate humidity with a warm hose, all adjusted to match your room's specific temperature.
1. Comfort Balance (humidity vs dryness)
There is always a tradeoff you have to manage. Too much humidity, combined with a cool hose, leads to condensation, while too little humidity leaves you waking up with a sore, dry throat. The golden rule here is to tweak only one setting at a time, making small steps so you can find the balance without swinging from one extreme to the other.
2. Stable Setup Defaults (simple targets)
While there is no single "perfect" number for everyone, these defaults work well for most people trying to stop rainout:
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Heated tubing turned on (if your machine has it) to maintain air temperature.
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Tube temperature is adjusted immediately if water droplets appear.
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Humidity is set to the lowest level that still prevents dryness symptoms.
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Hose routed carefully to avoid low dips where water can pool.
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Equipment positioned away from direct cold airflow, like fans or AC vents.
3. Maintenance and Nightly Habits
Good habits keep the system running smoothly. Always let your tubing dry completely after washing so you don't start the night with moisture already inside. Empty your water chamber in the morning to avoid stagnant water, and check for mask leaks that might be tricking you into pushing your humidity settings higher than necessary.
FAQ & Next Step
What is CPAP rainout?
CPAP rainout is condensation that forms when warm, humid air from your machine cools down inside the hose or mask. This temperature drop turns moisture back into liquid water droplets that can pool in the tube or splash onto your face, causing discomfort and wake-ups.
Why do I get water in my CPAP hose?
Water collects in your hose because the air traveling through it is warmer than the plastic tubing itself. When the humid airflow hits the cold walls of the hose, especially in a cool bedroom, it loses heat rapidly and condenses into water droplets instead of staying as vapor.
Should I change the tube temperature or humidity first?
Always increase your tube temperature first. Raising the tube temperature keeps the air warm enough to hold moisture all the way to your mask. If you lower the humidity first, you risk drying out your nose and throat without actually solving the condensation problem.
Does heated tubing prevent rainout?
Yes, heated tubing is the most effective tool for preventing rainout because it maintains a consistent air temperature from the machine to the mask. Keeping the hose warm, it prevents the cooling process that causes condensation, allowing you to use higher humidity settings comfortably.
Can I prevent rainout without buying anything?
Yes, you can often reduce rainout by tucking your hose under your blanket to keep it warm or by lowering your machine to the floor so water drains back into the humidifier. You can also try slightly warming up your bedroom or moving the equipment away from cold drafts, like fans or windows.
What should I do if there’s already water in the hose?
Disconnect the hose from your mask and machine immediately, then hold it high up to let gravity drain the water out. Reconnect it to your machine and run the air for a few minutes to dry out any remaining moisture before going back to sleep.
Is CPAP rainout dangerous?
Rainout is generally not dangerous, but it is disruptive and uncomfortable. The main risks are poor sleep quality due to wake-ups and potential skin irritation from a damp mask cushion. However, if water enters your airway, it can cause coughing or choking sensations that interrupt therapy.
Why is my CPAP making a gurgling noise?
A gurgling or bubbling noise means water has pooled in a low spot of your tubing, blocking the airflow like water in a straw. This usually happens when the hose sags below the level of the machine or mask. Straightening the hose or draining the water will stop the sound immediately.
Next Step: Your Plan for Tonight
If rainout has been waking you up, do not just hope it goes away. Tonight, start by increasing your tube temperature or turning on your heated tubing. If you do not have heated tubing, wrap your hose in a cover or tuck it under your sheets. Only lower your humidity if the temperature fix doesn't work.
Contact a clinician or DME if rainout persists despite adjustments, leading to ongoing wake-ups, discomfort, skin irritation, or challenges balancing humidification settings. The AASM clinical practice guideline emphasizes adequate follow-up and troubleshooting for PAP side effects to ensure efficacy and adherence, including issues like those from humidification.
References
Iara Rosemffet, CPAP Expert
21 Jan 2026•10 min read
