If you want streak-free windows, the type of water you use matters. Tap water contains minerals that can leave spots, streaks and residue behind as the water dries.
That is why many professional window cleaners use purified water such as deionised water or distilled water. Both are low-mineral options, but they are not always the best choice for the same job.
In this guide, we explain the difference between distilled water and deionised water for window cleaning, and which one is usually the better option.
👉 Shop deionised water for window cleaning
Why Tap Water Leaves Spots on Windows
Most UK tap water contains dissolved minerals such as calcium and magnesium. When the water evaporates, those minerals can remain on the glass.
This can leave:
- White marks
- Water spots
- Streaks
- Mineral residue
- A cloudy finish on glass
Using purified water helps reduce this because there are fewer dissolved minerals left behind after drying.
What Is Deionised Water?
Deionised water is purified using ion-exchange technology to remove charged mineral ions from water. This produces low-mineral water that is widely used for cleaning, rinsing and technical applications.
For window cleaning, deionised water is popular because it can dry with fewer marks and less residue than ordinary tap water.
👉 View our deionised water range
What Is Distilled Water?
Distilled water is purified through boiling and condensation. This process removes minerals, salts and many impurities, producing very low-mineral water.
Distilled water can be used for window cleaning, but it is more commonly chosen for appliances and sensitive uses such as CPAP machines, humidifiers, steam irons, batteries and laboratory applications.
For a full comparison, read our guide: Distilled vs Deionised Water — What’s the Difference?
Which Is Better for Window Cleaning?
For most window cleaning jobs, deionised water is the better and more practical choice.
It is commonly used for:
- Window cleaning
- Water-fed pole systems
- Glass cleaning
- Conservatories
- Solar panel cleaning
- Vehicle rinsing and detailing
Deionised water helps reduce mineral spotting and residue, making it ideal where a clean, streak-free finish is needed.
Can You Use Distilled Water for Window Cleaning?
Yes, distilled water can also be used for window cleaning because it contains very low mineral content.
However, for regular or professional window cleaning, deionised water is usually the preferred option because it is more commonly used for cleaning applications and can be more practical for larger volumes.
If you already use distilled water around the home, you may also find these guides helpful:
Distilled vs Deionised Water for Window Cleaning
| Water Type | Good for Window Cleaning? | Best Use |
|---|---|---|
| Tap Water | Not ideal | General household use, but may leave spots |
| Distilled Water | Yes | Small-scale cleaning, appliances and sensitive uses |
| Deionised Water | Best choice | Window cleaning, valeting, glass and professional cleaning |
Why Window Cleaners Use Deionised Water
Window cleaners often use deionised water because it helps reduce spotting and streaking without needing as many detergents or finishing products.
When used correctly, deionised water can help leave glass cleaner because fewer minerals remain behind after drying.
This makes it useful for:
- Domestic window cleaning rounds
- Commercial glass cleaning
- Water-fed pole systems
- Solar panel cleaning
- Final rinsing after washing
What Size Deionised Water Should You Buy?
The best size depends on how often you clean windows or glass.
- 5L bottles — useful for home use and small cleaning jobs
- 25L containers — suitable for regular cleaning, valeting and workshops
- 1000L IBCs — ideal for trade, industrial and higher-volume users
At The Somerset Clear Water Company, we supply deionised water in convenient retail and bulk sizes with fast UK delivery.
Why Buy from The Somerset Clear Water Company?
We manufacture and bottle purified water in Somerset, supplying both retail and trade customers across the UK.
Customers choose us for:
- UK manufactured deionised water
- Retail and bulk supply options
- 5L, 25L and 1000L IBC sizes
- Fast UK delivery
- Supply for domestic, trade and industrial users
If you are unsure which purified water you need, start with our anchor guide: Distilled vs Deionised Water — What’s the Difference?
Frequently Asked Questions
Is deionised water good for window cleaning?
Yes. Deionised water is commonly used for window cleaning because it helps reduce mineral spotting, streaks and residue on glass.
Is distilled water good for window cleaning?
Yes, distilled water can be used for window cleaning because it has very low mineral content, but deionised water is usually the more practical choice for regular or professional cleaning.
Why does tap water leave marks on windows?
Tap water contains dissolved minerals such as calcium and magnesium. When the water dries, these minerals can remain on the glass and leave spots or streaks.
Which is better for window cleaning, distilled or deionised water?
For most window cleaning applications, deionised water is usually better because it is widely used for low-residue cleaning, glass cleaning and water-fed pole systems.
Can deionised water be used for solar panel cleaning?
Yes. Deionised water is often used for solar panel cleaning because it helps reduce mineral residue and spotting.
Need purified water for streak-free cleaning?
👉 Shop deionised water here