If you use a CPAP machine with a humidifier chamber, the type of water you add matters. Using the wrong water can lead to mineral build-up, residue, more cleaning, and potentially reduced performance over time.
For most CPAP humidifiers, distilled water is the best choice because it contains very low levels of dissolved minerals and helps keep the water chamber cleaner.
👉 Shop distilled water for CPAP machines
Why Water Choice Matters in CPAP Machines
Many CPAP machines use a heated humidifier to add moisture to the airflow. This can make therapy more comfortable by helping reduce dryness in the nose, throat, and mouth.
However, when water is heated and evaporated, any minerals in that water can be left behind inside the chamber.
Over time, this can lead to:
- White residue inside the humidifier chamber
- Limescale build-up
- More frequent cleaning
- Reduced appliance hygiene and performance
- Shorter lifespan of removable parts
Can You Use Tap Water in a CPAP Machine?
Tap water is not ideal for CPAP humidifier chambers, especially in hard water areas of the UK.
UK tap water o ften contains dissolved minerals such as calcium and magnesium. These minerals are fine for normal drinking water, but they can leave residue when used in appliances that heat or evaporate water.
In a CPAP humidifier, tap water may cause:
- Scale inside the water chamber
- Cloudy residue
- More difficult cleaning
- Mineral deposits around the chamber
If you are comparing this with humidifier use generally, you may also find our guide useful: Why Is My Humidifier Leaving White Dust?
Can You Use Boiled Water in a CPAP Machine?
Boiled water is not the same as distilled water.
Boiling water can kill bacteria, but it does not remove the minerals that cause limescale and residue. That means boiled tap water may still leave mineral deposits inside your CPAP humidifier chamber.
For a full explanation, read our guide: Is Distilled Water Just Boiled Water?
Why Distilled Water Is Best for CPAP Humidifiers
Distilled water is purified through boiling and condensation. This process removes minerals, salts, and many impurities, leaving water with very low dissolved solids.
Using distilled water in a CPAP humidifier can help:
- Reduce limescale build-up
- Prevent mineral residue
- Keep the water chamber cleaner
- Reduce cleaning effort
- Support better long-term appliance care
👉 Browse distilled water for CPAP users
Distilled vs Deionised Water for CPAP Machines
Distilled and deionised water are both highly purified, but they are made differently and are not always used for the same purpose.
For CPAP humidifier chambers, distilled water is generally the better choice because it is more suitable for household and health-related appliance use.
Deionised water is commonly used for technical, industrial, cleaning, and automotive applications, but distilled water is usually preferred for CPAP machines, humidifiers, steam irons, and similar appliances.
For a full comparison, read our anchor guide: Distilled vs Deionised Water — What’s the Difference?
CPAP Water Comparison Table
| Water Type | Good for CPAP? | Key Issue |
|---|---|---|
| Tap Water | Not ideal | Contains minerals that can cause residue and scale |
| Boiled Water | Not ideal | Still contains minerals after boiling |
| Deionised Water | Usually not first choice | Better suited to cleaning, technical, and industrial uses |
| Distilled Water | Best option | Very low mineral content and better for appliance care |
How Often Should You Change CPAP Water?
For hygiene, CPAP water should usually be emptied and refreshed daily. Always follow your machine manufacturer’s instructions and cleaning guidance.
Even when using distilled water, it is good practice to:
- Empty the chamber each day
- Rinse and clean the chamber regularly
- Allow parts to air dry
- Replace components as recommended by the manufacturer
Distilled water helps reduce mineral build-up, but it does not replace regular cleaning.
What Size Distilled Water Is Best for CPAP Users?
If you use your CPAP humidifier every night, it is worth keeping a reliable supply of distilled water at home.
- 5L Distilled Water – Single Bottle — ideal for occasional use or smaller appliances
- 2 Pack 5L (10L Total) — a handy starter supply for regular users
- 3 Pack 5L (15L Total) — popular for regular household use
- 4 Pack 5L (20L Total) — great value for frequent users or multiple appliances
Many customers also use distilled water for humidifiers, steam irons, and other appliances where limescale is a concern.
Read more: Best Water for Humidifiers UK.
Why Buy Distilled Water from The Somerset Clear Water Company?
At The Somerset Clear Water Company, we manufacture distilled water in Somerset and supply homes, healthcare users, trade customers, and businesses across the UK.
Customers choose us for:
- UK-made distilled water
- Lab-tested purity
- Reliable quality
- Convenient 5L, multipack, and 25L sizes
- Fast UK delivery
👉 Shop distilled water for CPAP machines
Shop Our Distilled Water for CPAP Machines
| Product | Best For |
|---|---|
| 5 Litre Distilled Water – Single Bottle (Lab Tested) | Occasional or light CPAP use |
| 2 Pack 5L Distilled Water – 10L Total (Lab Tested) | Regular use, 2–4 week supply |
| 3 Pack 5L Distilled Water – 15L Total (Lab Tested) | Regular users, best-selling size |
| 4 Pack 5L Distilled Water – 20L Total (Great Value) | Frequent users or multiple appliances |
Frequently Asked Questions
What water should I use in a CPAP machine?
Distilled water is generally the best option for CPAP humidifier chambers because it contains very low levels of dissolved minerals and helps reduce residue and limescale.
Can I use tap water in my CPAP machine?
Tap water is not ideal, especially in hard water areas, because it contains minerals that can leave residue and scale inside the water chamber.
Can I use boiled water instead of distilled water in a CPAP machine?
Boiled water is not the same as distilled water. Boiling does not remove minerals, so boiled water can still cause limescale and residue.
Can I use deionised water in a CPAP machine?
Distilled water is generally preferred for CPAP humidifiers. Deionised water is more commonly used for cleaning, technical, automotive, and industrial applications.
How often should CPAP water be changed?
CPAP humidifier water should usually be emptied and replaced daily. Always follow your machine manufacturer’s cleaning and maintenance instructions.
Need distilled water for your CPAP machine?
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