Understanding Purified Water: Distilled vs. Deionized
Not all pure water is created equal, and for human consumption, the distinction between distilled and deionized (DI) water is critical. While both processes remove impurities, they do so differently and with vastly different implications for your health and taste buds. Knowing which is which is the first step in making an informed hydration choice.
The Distillation Process
Distillation mimics the earth’s natural water cycle. Water is boiled into steam, and as it vaporizes, it leaves behind minerals, most contaminants, bacteria, and viruses. The collected steam is then cooled and condensed back into a liquid state. The final product is highly pure water, consisting solely of hydrogen and oxygen, which results in its characteristically 'flat' taste.
- Method: Boiling and condensation.
- Removes: Minerals, most biological contaminants (bacteria, viruses), heavy metals, and chemicals with higher boiling points.
- Potential Drawback: Can leave behind volatile organic compounds (VOCs) with lower boiling points, although carbon filtration can mitigate this.
The Deionization Process
Deionization, or DI, is a chemical process that uses ion exchange resins to remove mineral salts from water. These resins are charged with positive and negative ions ($H^{+}$ and $OH^{-}$) that attract and bind to the corresponding mineral ions ($Ca^{2+}, Mg^{2+}, Na^{+}$) present in the water. The result is water with very few charged particles, making it highly non-conductive.
- Method: Ion exchange using charged resins.
- Removes: Mineral ions (calcium, magnesium, sodium, etc.).
- Potential Drawback: Does not remove uncharged contaminants like bacteria, viruses, or many organic compounds.
The Verdict: Drinking Distilled vs. Deionized Water
While distilled water is safe to drink, deionized water is not recommended for human consumption. The fundamental difference lies in what each process removes and, crucially, what it leaves behind. Distillation removes both charged minerals and biological threats, ensuring a purer, albeit tasteless, final product. Deionization is a chemical process that, by itself, doesn't address microbiological safety.
Why Distilled Water is Generally Safe (with caveats)
For a healthy individual with a balanced diet, drinking distilled water in moderation poses no significant health risks. The body gets the vast majority of its minerals and electrolytes from food, not water. However, long-term, exclusive consumption of distilled water has a few minor drawbacks:
- Flat Taste: The absence of minerals results in a tasteless and unappealing flavor that can lead to reduced water intake.
- Lack of Mineral Contribution: While not a primary source, tap water provides a small contribution of essential minerals like calcium and magnesium.
- Electrolyte Dilution (Extreme Cases): For those with intense exercise or illness, drinking large amounts of mineral-free water could, theoretically, dilute electrolytes. However, this is more likely in malnourished or dehydrated states where electrolyte solutions would be needed regardless.
Why You Should Avoid Drinking Deionized Water
Deionized water is designed for industrial and laboratory use where ion-free water is critical for processes like cooling electronics or manufacturing pharmaceuticals. Its properties make it unsafe and unsuited for regular human consumption:
- Potential for Contaminants: As the deionization process only removes ions, it can leave behind harmful bacteria, viruses, and uncharged organic compounds. If the source water was untreated, these could pose a serious health risk.
- Highly Corrosive: Lacking minerals, deionized water is a highly aggressive solvent. This means it can leach trace amounts of toxic metals from pipes, containers, or plumbing as it moves through a system, leading to potentially harmful ingestion. The World Health Organization has warned against its long-term consumption for this reason.
Should You Re-mineralize Purified Water?
If you have access to a reliable municipal water source, re-mineralizing is unnecessary. However, if you are concerned about long-term consumption of purified water or want to improve its taste, re-mineralizing is an option. This can be done with mineral drops, sea salt, or specialized filters that add beneficial minerals back into the water.
Comparison: Distilled Water vs. Deionized Water
| Feature | Distilled Water | Deionized Water |
|---|---|---|
| Purification Method | Boiling and condensation | Ion exchange resins |
| Removes Minerals? | Yes, nearly 100% | Yes, nearly 100% of ions |
| Removes Bacteria & Viruses? | Yes, most are removed | No, uncharged pathogens remain |
| Effect on Taste | Flat or tasteless | Flat, sometimes unpleasant |
| Safety for Drinking | Safe (in moderation with balanced diet) | Not recommended for drinking |
| Aggressive/Corrosive | Mildly, less than DI water | Highly corrosive (leaches metals) |
| Typical Use Case | Appliances (irons, humidifiers), some lab work | Industrial, scientific, and pharmaceutical |
Conclusion
While the concept of super-pure water is appealing, the reality for drinking is more nuanced. Distilled water is a safe choice, particularly for temporary use or specific applications like appliances, as long as you maintain a balanced diet for mineral intake. However, its 'flat' taste may be unappealing for everyday consumption. On the other hand, deionized water is not suitable for drinking due to its failure to remove biological contaminants and its corrosive nature, which can cause it to leach metals from storage and delivery systems. For the average person seeking safe and healthy drinking water, a quality filter that retains beneficial minerals or simply opting for safe tap water is the best course of action.
Key takeaways
- Distilled water is safe for drinking in moderation, provided you get essential minerals from your diet.
- Deionized water is not safe for drinking due to potential bacterial contamination and its corrosive nature.
- The purification processes differ: Distillation uses boiling, while deionization uses ion exchange resins.
- Mineral-free water tastes 'flat', which can lead to drinking less water than necessary.
- For everyday hydration, filtered tap water or mineral water is a better choice to ensure you receive trace minerals.
- Distilled water is ideal for appliances like steam irons and humidifiers to prevent mineral buildup.
- Deionized water is primarily for industrial and laboratory applications requiring ion-free solutions.
Faqs
Q: What is the main difference between distilled and deionized water? A: The main difference lies in their purification process and what they remove. Distilled water is boiled to remove almost all impurities, including minerals and most pathogens. Deionized water uses ion exchange to remove charged mineral ions but leaves uncharged contaminants like bacteria and viruses.
Q: Is it bad to drink distilled water all the time? A: For healthy individuals with a balanced diet, it is not inherently harmful. However, since it lacks minerals like calcium and magnesium, long-term exclusive consumption is not recommended, and some people find its flat taste unappealing.
Q: Why shouldn't I drink deionized water? A: Deionized water is not safe for drinking because the purification process does not remove bacteria or viruses. Furthermore, its aggressive, mineral-free nature can cause it to leach metals and other harmful substances from pipes and containers.
Q: Does drinking distilled water leach minerals from your body? A: This is a common myth. While pure water has a high solvency, a healthy body regulates its mineral balance effectively, and we get most of our minerals from food. There is no evidence that drinking distilled water pulls essential minerals from the body's tissues.
Q: Can I use deionized water in my humidifier? A: No, it is better to use distilled water. While both are low in minerals and will prevent scale buildup, DI water is not sterile and may contain bacteria or other microbes that can be aerosolized into the air by the humidifier.
Q: What is the best type of water to drink regularly? A: For most people, safe tap water or filtered water is the best choice. These options retain beneficial minerals while removing harmful contaminants. High-quality filtered or spring water provides the best of both worlds.
Q: How can I tell if water is distilled or deionized? A: Visually, they are identical. The primary way to tell is by testing its electrical conductivity. Deionized water is a poor conductor of electricity due to the absence of ions, and specialized equipment is needed for confirmation. Distilled water is also very low in conductivity.
Q: Can I cook with distilled water? A: Yes, you can cook with distilled water. It will not have a significant impact on your mineral intake, as the body primarily absorbs minerals from food.
Q: Is it necessary to remineralize purified water? A: For those with a balanced diet, it is not strictly necessary. However, re-mineralizing can improve the flavor of the water and ensure a baseline level of mineral intake. Remineralization kits or adding mineral drops are simple ways to do this.
