Distilled water is water that has been purified by boiling it into steam and condensing the steam back into liquid in a separate container. This process removes dissolved minerals, most bacteria, and many organic contaminants. The result is water with very low ionic content, but it is not the same as deionised or ultrapure water and is not suitable for all laboratory applications.
Despite being one of the oldest purification methods, distilled water is still widely used in Australian laboratories, medical facilities, and industrial processes. However, many labs have moved to modern purification systems that combine reverse osmosis, deionisation, and UV treatment because distillation alone has limitations that can affect sensitive analytical work.
In This Guide
How It's Made · What It Removes (and Doesn't) · Laboratory Uses · Limitations · Distilled vs Deionised vs Demineralised · Common Mistakes · FAQ
How Distilled Water Is Made
Step 1: Tap water or source water is heated to boiling point (100 degrees Celsius).
Step 2: The steam rises, leaving behind dissolved minerals, salts, heavy metals, and most microorganisms that cannot evaporate.
Step 3: The steam is collected in a condenser, cooled, and converted back into liquid water.
Step 4: The condensed water is collected in a clean container. This is distilled water.
The process is simple but energy-intensive. A laboratory water still typically produces 2 to 8 litres per hour, which is significantly slower than modern reverse osmosis or deionisation systems.
What Distillation Removes (and What It Doesn't)
| Contaminant Type | Removed? | Notes |
|---|---|---|
| Dissolved minerals and salts | Yes | Calcium, magnesium, sodium, chloride left behind |
| Heavy metals | Yes | Lead, mercury, arsenic do not evaporate at 100 degrees |
| Bacteria | Yes | Killed by boiling, but recontamination can occur during storage |
| Particulates | Yes | Sediment remains in the boiling chamber |
| Volatile organic compounds (VOCs) | No | VOCs evaporate with the steam and recondense into the distillate |
| Dissolved gases (CO2, O2) | No | CO2 dissolves back, lowering pH to around 5.5 to 6.5 |
Key point: Distilled water is not the same as ultrapure water. It removes most inorganic contaminants effectively but leaves volatile organics and dissolved gases behind. For HPLC, PCR, and trace metal analysis, modern multi-stage purification systems like the Labconco WaterPro PS are required.
Laboratory Uses for Distilled Water
Glassware rinsing: Final rinse for general laboratory glassware to remove tap water mineral residues. For trace analysis glassware, use Type I or II water instead. See our guide on how to clean lab glassware properly.
Autoclave feed: Prevents mineral scale buildup on the autoclave chamber and sterilised instruments.
General reagent preparation: Suitable for preparing non-critical buffers, solutions, and dilutions where trace-level contamination is not a concern.
Humidifiers and water baths: Prevents mineral deposits in temperature-controlled equipment.
Teaching laboratories: Adequate for educational experiments where high analytical precision is not required.
When Distilled Water Is Not Enough
Critical Warning
Do not use distilled water for HPLC, LC-MS, ICP-MS, PCR, or cell culture. Volatile organic compounds that co-distil with the water create baseline noise in chromatography, inhibit enzymatic reactions, and introduce contaminants into cell cultures. These applications require Type I ultrapure water (18.2 megaohm-cm resistivity).
Slow production: A typical still produces 2 to 8 L/hr. A Labconco WaterPro system produces purified water on demand at significantly higher flow rates.
High energy consumption: Boiling water continuously requires substantial electricity compared to RO and deionisation systems.
Storage degradation: Distilled water absorbs CO2 from air within hours, lowering pH. It also picks up contaminants from storage containers.
Does not meet Type I or II specifications: Distilled water alone does not achieve the resistivity, TOC, or microbial limits required for Type I (18.2 megaohm-cm) or Type II (1 to 10 megaohm-cm) laboratory water grades.
Distilled vs Deionised vs Demineralised Water
| Factor | Distilled | Deionised | Demineralised |
|---|---|---|---|
| Method | Boiling + condensation | Ion exchange resins or EDI | Ion exchange resins |
| Removes ions | Yes (most) | Yes (extremely effective) | Yes (very effective) |
| Removes bacteria | Yes | No | No |
| Removes VOCs | No | No | No |
| Best for | Autoclaves, rinsing, general prep | Analytical chemistry, high-purity work | Industrial processes, general lab use |
For a detailed comparison including water grades and application mapping, see our full guide on distilled vs demineralised vs deionised water.
Need to move beyond distillation? Browse our Labconco WaterPro water purification range for Type I and Type II laboratory water.
Common Mistakes with Distilled Water
- Assuming distilled = ultrapure: Distilled water is not Type I water. It still contains VOCs and dissolved gases. Using it for HPLC or PCR will produce unreliable results.
- Storing it too long: Distilled water absorbs CO2 from the air within hours, dropping pH to 5.5 to 6.5. It also leaches contaminants from plastic containers. Use freshly produced water whenever possible.
- Using it for cell culture: While distillation kills bacteria, it does not remove endotoxins or organic contaminants. Cell culture requires Type I water with ultrafiltration.
- Not maintaining the still: Scale builds up in the boiling chamber, reducing efficiency. Regular descaling is essential, especially in areas with hard water like Perth and Adelaide.
- Using tap water for final rinses to save cost: Even final rinses with tap water leave mineral residues on glassware that contaminate the next experiment.
Related Guides
Distilled vs Demineralised vs Deionised Water · How to Clean Lab Glassware · What Is Borosilicate Glass?
Frequently Asked Questions
What is distilled water?
Distilled water is water purified by boiling and condensation. The steam is collected and cooled, leaving behind dissolved minerals, heavy metals, bacteria, and particulates. The result is water with very low mineral content, suitable for autoclaves, general lab rinsing, and non-critical reagent preparation.
Is distilled water safe to drink?
Yes. Distilled water is safe to drink. It simply lacks the minerals found in tap water. However, it has a flat taste because minerals contribute to the flavour of drinking water. In Australia, tap water regulated under the Australian Drinking Water Guidelines is safe and more practical for drinking.
Can I use distilled water for HPLC?
No. Distilled water contains volatile organic compounds that co-distil with the steam. These create baseline noise and ghost peaks in HPLC chromatograms. HPLC requires Type I ultrapure water with 18.2 megaohm-cm resistivity and low Total Organic Carbon.
What is the pH of distilled water?
Freshly produced distilled water has a pH close to 7.0. However, it rapidly absorbs CO2 from the air, which forms carbonic acid and drops the pH to approximately 5.5 to 6.5 within hours. This is normal and expected.
What is the difference between distilled and deionised water?
Distilled water is purified by boiling and condensation. It removes ions, bacteria, and particles but not volatile organics. Deionised water is purified by ion exchange resins. It removes ions very effectively but does not remove bacteria or organics. See our full guide on distilled vs demineralised vs deionised water.
Where can I buy water purification systems in Australia?
John Morris Group supplies Labconco WaterPro water purification systems that produce Type I and Type II laboratory water from tap water. Systems range from the WaterPro RO for general lab use to the WaterPro PS for Type I ultrapure water polishing. Call 1300 501 555.
Need More Than Distilled Water?
Modern laboratories need Type I and Type II water on demand. Labconco WaterPro systems produce ultrapure and pure water, replacing stills, deionisers, and bottled water purchases.
Call 1300 501 555 or browse our Labconco WaterPro range online.
