If you use a CPAP machine for sleep apnoea, you may already know that water quality matters — but understanding why can help you protect your equipment, improve comfort, and avoid unnecessary maintenance or health issues.
In this guide, we’ll explain:
- What type of water is best for CPAP machines
- Why distilled water is recommended
- What happens if you use tap or bottled water
- Where to buy high-quality distilled water in the UK
Why Do CPAP Machines Need Water at All?
Most CPAP machines include a heated humidifier, designed to:
- Prevent dry mouth and throat
- Reduce nasal irritation
- Improve overall comfort during therapy
The humidifier chamber heats water to add moisture to the airflow — and this is where water purity becomes critical.
What Is the Best Water to Use in a CPAP Machine?
Distilled water is the manufacturer-recommended choice for almost all CPAP machines.
For CPAP users, choosing the right water is essential — using high-purity distilled water helps protect your machine and improve therapy comfort.
👉 View distilled water suitable for CPAP machines
Why Distilled Water Is Recommended for CPAP Machines
Distilled water has been purified through distillation, removing:
- Minerals (calcium, magnesium, limescale)
- Bacteria and microorganisms
- Dissolved solids and impurities
This matters because:
- Minerals cause limescale build-up inside the humidifier chamber
- Build-up can shorten the lifespan of your CPAP machine
- Residue can affect hygiene and cleaning frequency
For regular CPAP use, many customers choose to buy distilled water specifically for CPAP machines to minimise maintenance and ensure consistent performance.
👉 Shop distilled water for CPAP use
What Happens If You Use Tap Water in a CPAP Machine?
Using tap water may seem harmless, but it often contains:
- Dissolved minerals (hardness varies by region)
- Trace metals
- Microorganisms
Over time, this can lead to:
- White mineral residue inside the humidifier
- Increased cleaning requirements
- Potential damage to internal components
Manufacturers generally advise against using tap water for long-term CPAP use.
Is Bottled or Filtered Water Safe for CPAP Machines?
Bottled, filtered, or spring water is not the same as distilled water.
Even filtered water usually still contains:
- Dissolved minerals
- Trace salts
If you’re unsure how distilled water compares to other purified options, you may find our guide on distilled vs deionised water helpful.
👉 Read: Distilled vs Deionised Water – What’s the Difference?
Can You Use Deionised Water in a CPAP Machine?
Deionised water has had charged ions removed, but it may still contain:
- Organic compounds
- Microorganisms
While it’s suitable for some technical applications, distilled water remains the safest and most widely recommended option for CPAP humidifiers.
How Often Should You Change CPAP Water?
Best practice is to:
- Empty the humidifier chamber daily
- Refill with fresh distilled water each night
- Clean the chamber regularly according to manufacturer guidance
Using distilled water helps reduce residue, making cleaning easier and more effective.
Which Water Is Best for a CPAP Machine?
Not all water types are equal when used in a CPAP humidifier. Here’s how they compare:
| Water Type | Contains Minerals? | Risk of Limescale | Recommended for CPAP? |
|---|---|---|---|
| Tap Water | Yes (varies by region) | High | ❌ Not recommended long-term |
| Bottled / Filtered Water | Yes | Medium to High | ❌ Not recommended |
| Distilled Water | No (mineral-free) | Very Low | ✅ Recommended |
Looking for reliable UK-manufactured distilled water?
Shop distilled water suitable for CPAP machines here →
Where Can You Buy Distilled Water for CPAP Machines in the UK?
Many CPAP users also ask practical questions about availability, safety and suitability of distilled water in the UK. Here are clear answers to the most common concerns.
Can any distilled water be used for CPAP?
Yes — as long as it is genuinely distilled and mineral-free. Check the label clearly states distilled water (not deionised only), and avoid mineral/spring/filtered water for long-term CPAP humidifier use.
Can I buy distilled water in the supermarket in the UK?
Usually not. Most UK supermarkets don’t stock true distilled water — they mainly sell mineral, spring or filtered water, which still contains dissolved minerals that can leave residue in your humidifier chamber.
Can I make my own distilled water for CPAP?
Home distillation is possible, but it’s time-consuming and purity can vary. For a medical device used nightly, professionally distilled water is the most consistent option.
Do pharmacies carry distilled water?
Some pharmacies may sell small quantities of purified/sterile water, but availability and sizes vary and it can be pricey for daily use. For regular CPAP use, buying larger containers from a specialist supplier is usually more practical.
Not all distilled water is the same. For CPAP use, it’s important to choose:
- High-purity distilled water
- Reliable UK manufacturing
- Consistent supply for daily use
Our UK-manufactured distilled water is produced for high-purity applications and is suitable for CPAP machines, humidifiers, and medical equipment.
👉 Buy distilled water for CPAP machines
Technical Information and Safety Documentation
We provide full documentation for our water products, including certificates of analysis and safety data sheets, giving you confidence in quality and compliance.
👉 View our technical documentation section
Frequently Asked Questions About CPAP Water
Can I use boiled water in a CPAP machine?
No. Boiling kills bacteria but does not remove minerals, so limescale build-up can still occur.
Why does my CPAP humidifier get white residue?
This is mineral residue from tap or bottled water. Using distilled water prevents this.
How do you clean a CPAP humidifier chamber?
Rinse the chamber regularly and clean it according to the manufacturer’s instructions. Mineral build-up is more likely when using tap or mineral-rich water.
Does distilled water help protect CPAP equipment?
Yes. Distilled water contains very low minerals, reducing limescale deposits and helping extend the lifespan of the humidifier chamber.
Final tip
Using the correct water in your CPAP machine is a small change that can make a big difference to comfort, hygiene, and long-term equipment care.
