CPAP Rainout: Causes and Quick Fixes

Rainout is water from your humidifier condensing inside a hose that is cooler than the warm, moist air it carries, then dripping or gurgling into your mask. The makers' own manuals give the same fixes, which are to keep the machine lower than your head, turn the humidity down a level, and keep the hose warm with a heated tube or a higher tube temperature. Already using a heated tube? The section after Step 3 covers what each maker says to try next.

Step 1: Put the Machine Lower Than Your Head

Every maker's manual gives this rule, and it costs nothing. Water that condenses in the hose runs downhill. With the machine lower than your head, it runs back toward the water chamber. With the machine higher, it runs toward your face.

• ResMed's AirSense 11 and AirSense 10 guides both say to place the machine on a level surface lower than your head "to prevent the mask and air tubing from filling with water."
• Philips' DreamStation humidifier manual and DreamStation 2 manual both say the humidifier must always be "positioned below the breathing circuit connection at the mask."
• React Health's Luna G3 manual says to place it lower than your head "so that the condensation flows back to the water chamber rather than remain in the tubing causing rainout."

If your nightstand is taller than your mattress, move the machine to a lower shelf or a small stand beside the bed.

Step 2: Turn the Humidity Down One Level

More moisture in the air means more water available to condense. Every maker's manual gives the same answer for water in the hose or mask, which is to lower the humidity setting.

• ResMed AirSense 10 and 11. Humidity runs from Off to 8. The guides say, "If you are getting any moisture in your mask, turn down the humidity."
• Philips DreamStation. The humidifier manual lists "Excessive condensation in the tubing" with the fix "Reduce the humidity level setting." On the DreamStation 2, humidity runs from 0 to 5.
• Luna G3. Five humidity levels. The manual says to "lower the humidifier setting level" when water collects in the tube.

Go down one level at a time and give each change a night or two. The Luna G3 manual offers a simple check. A few droplets in the tube in the morning means the humidity is about right. A lot of water in the tube or mask means it is set too high.

If a lower setting leaves your nose or mouth dry, keep the humidity and warm the hose instead (Step 3). For finding your level, see CPAP humidity settings.

Step 3: Keep the Hose Warm

Condensation forms where the hose is colder than the air inside it, so a warmer hose means less water. A heated tube keeps the whole length warm. Use the one your machine's maker lists for your model, or ask your equipment supplier which one fits.

• ResMed AirSense 11. With the ClimateLineAir 11 heated tube and HumidAir 11 tub attached, Climate Control Auto is the default. ResMed says Auto "protects against rainout" and sets the tube to 80ºF, which you can change anywhere from 60 to 86ºF.
• ResMed AirSense 10. The guide suggests ClimateLineAir heated tubing if you keep getting moisture in your mask, and points to the ClimateLineAir user guide for its settings.
• Philips DreamStation. The heated tube has its own setting, and the manual says a tube that is not warming may have it set to zero. On the DreamStation 2 it runs from 0 to 5, and the setting only shows when a heated tube is connected and your equipment provider has turned it on. Both models' heated tubes run from 60 to 86ºF.
• Luna G3. The manual lists "using a heated tube, or increasing your heated tube setting" among the ways to reduce condensation, with five heat levels.

Already Have a Heated Tube and Still Get Water?

The makers' answers here are specific.

• AirSense 11 in Manual mode. ResMed says, "Rainout protection is not guaranteed. If rainout does occur, first try increasing the tube temperature." If the air then feels too warm and rainout continues, decrease the humidity. You can also switch Climate Control back to Auto, which ResMed recommends.
• AirSense 11 in Auto mode. Auto manages the humidity for you, and the tube temperature is the setting you can change. Raise it a few degrees from the 80ºF default, up to 86ºF.
• AirSense 11, either mode. The troubleshooting table lists two causes for "droplets of water on my nose, in the mask and air tubing." Humidity may be too high, so decrease it, and the tube temperature may be too low, so increase it.
• DreamStation. Check that the heated tube setting is not set to zero, the cause the humidifier manual lists for a tube that is not warming. On a DreamStation 2, if you see no heated tube setting at all, ask your equipment provider, who controls whether it shows.
• Any machine. Check Step 1 again. A heated tube cannot stop water from running downhill toward your face if the machine sits higher than your head.

Step 4: Keep Cold Air Off the Hose

The colder the room, the more the hose cools. The Luna G3 manual names "cold ambient room temperature and high humidifier output" as the cause of condensation in the tubing. Philips adds a second cause, a machine placed too close to air conditioning, and the DreamStation 2 manual says to keep the machine away from "forced air vents, radiators, air conditioners."

• Move the machine and hose away from air conditioning vents, fans, drafty windows and cold outside walls.
• Keep the hose off cold surfaces such as a window sill or the floor.
• If you like a cold bedroom, expect more rainout in winter, and use the steps above to make up for it.

Step 5: Fill and Move the Water Chamber With Care

Not all water in the hose is condensation. Water from the chamber itself can get into the tubing, and it looks just like rainout.

• Fill only to the maximum line. The AirSense 11 guide says, "Do not overfill the humidifier tub as water may enter the device and air tubing." Philips gives the same warning, and the Luna G3 manual says to make sure the water "does not exceed the maximum water level line."
• Do not move or tilt the machine with water in it. Philips says, "Do not move the humidifier while the water tank has water in it," and the Luna G3 manual says to "avoid moving or tilting the device when the water chamber has water in it." Empty the chamber before you carry the machine anywhere.
• Leave it plugged in after you stop. The AirSense 10 keeps blowing a little air for 30 minutes after therapy ends "in order to avoid condensation in the air tubing." Unplugging it right away skips that.

Step 6: Drain the Hose When It Happens

When you wake up to water in the hose, take the hose off and drain it before you go back to sleep. The Luna G3 manual says, "If condensation is present in the tube, remove and drain the tube. Lower the humidifier setting level." On an AirSense 11, water in the tubing can also stop the machine with an error, and ResMed's fix is to empty the tubing, then unplug the power and plug it back in.

Let the hose dry fully during the day. Standing water is worth a closer look at your cleaning routine.

Why Rainout Is Worse in Winter

Rainout is a temperature gap, and winter widens it. Bedrooms cool off at night, the hose cools with them, and dry indoor air can make you want more humidity. More moisture in a colder hose means more water. If you only get rainout in the colder months, one approach is to raise the tube temperature or lower the humidity a step when the weather turns, then try your usual settings again in spring.

How Rainout Affects Your Therapy

Rainout is usually a comfort problem rather than a fault in the machine. It can still cost you sleep and therapy time.

• It can wake you up. Water on your face in the night is hard to sleep through, and it can lead to taking the mask off and leaving it off.
• It leaves standing water. A hose that stays wet needs drying and regular cleaning.

Checking Your Data

CPAP Clarity shows the humidity setting (a level, Auto or Off) and the tube type your card recorded, where your machine writes them, so you can check what it was set to. If it lists a different tube than the one you use, check the machine's Tube Type setting. After a change, your leak and usage across the next few nights show whether the mask stayed on and sealed.

When to Talk to Your Provider

Rainout is an equipment and comfort issue, and humidity and tube temperature are comfort settings you can change yourself, as the makers' guides describe. Talk to your sleep physician or equipment supplier if:

• Rainout is making you skip nights or take the mask off. Any drop in use is worth raising.
• You need a heated tube or a different humidifier part. Your supplier can tell you which one fits your machine.
• Dryness and rainout both persist however you set humidity and tube temperature. Your provider can look at your settings as a whole.
• You see mold or notice a smell in the hose or chamber despite regular cleaning.

For other problems, such as leak, pressure that feels wrong, mask pain or nights with no data, the CPAP troubleshooting guide works through them symptom by symptom.

Primary Sources

• ResMed AirSense 11 user guide (opens in new tab) - Climate Control Auto and Manual, tube temperature range, humidity levels, placement, overfilling and the troubleshooting table.
• ResMed AirSense 10 user guide (opens in new tab) - Humidity, ClimateLineAir, placement, overfilling and the 30-minute cool-down.
• Philips DreamStation Heated Humidifier user manual (opens in new tab) - Placement, overfilling, moving the humidifier, tube temperature range and the condensation troubleshooting rows.
• Philips DreamStation 2 Advanced user manual (opens in new tab) - Placement, keeping the machine away from vents and air conditioners, humidity and heated tube settings, and the heated tube temperature range.
• React Health Luna G3 APAP user manual (opens in new tab) - Placement, condensation causes and fixes, draining the tube, and moving the machine.