Understanding the Concept of "Pure" Water
In chemistry, "pure" water, or $H_2O$, refers to water containing only hydrogen and oxygen molecules, with no dissolved minerals, contaminants, or other impurities. From this scientific perspective, distilled water is the purest form of water readily available, as the process of distillation most effectively separates water from everything else. However, for drinking purposes, the purest water isn't necessarily the best or healthiest, because the very minerals stripped away during purification are vital for human health.
The Distillation Process: Achieving Purity
Distillation involves boiling water to create steam and then condensing that steam back into a liquid state in a separate container. As the water boils and turns into vapor, it leaves behind virtually all contaminants, including dissolved minerals, bacteria, viruses, and heavy metals. This process effectively mimics the earth's natural hydrologic cycle, creating a product that is nearly 100% pure $H_2O$.
Limitations and Considerations of Distilled Water
Despite its purity, distilled water is not widely recommended for long-term daily consumption due to its complete lack of essential minerals like calcium and magnesium. Some studies have linked the long-term consumption of demineralized water with negative health outcomes. Furthermore, the lack of minerals gives it a flat, almost tasteless quality that many people find unappealing.
Other Purification Methods and Their Purity Levels
Beyond distillation, other methods can produce highly pure water, each with different levels of efficacy and implications for drinking:
- Reverse Osmosis (RO): This process forces water through a semi-permeable membrane that filters out most dissolved solids, including ions and larger molecules. RO water is very pure, but typically not as pure as distilled water, and many residential systems include a remineralization stage to improve taste and health benefits.
- Deionization (DI): Using ion-exchange resins, this method removes mineral ions from water. DI water is exceptionally pure in terms of ion content and is often used in laboratories and microelectronics manufacturing, but it does not effectively remove uncharged organic molecules or microbes.
- Standard Filtration (Carbon Filters): Common household filters use activated carbon to remove chlorine, sediment, and other organic contaminants that affect taste and odor. While improving the water quality, it does not achieve the same level of purity as distillation or RO.
- Ultraviolet (UV) Oxidation: UV light is used to disinfect water by killing bacteria, viruses, and other pathogens. This process purifies the water microbiologically but does not remove dissolved solids or other chemical contaminants.
Comparison of Water Purification Methods
| Feature | Distilled Water | Reverse Osmosis (RO) | Deionized (DI) Water | Tap Water (Filtered) |
|---|---|---|---|---|
| Level of Purity | Extremely high; near 100% pure $H_2O$. | Very high; removes most contaminants. | Extremely high; removes almost all mineral ions. | Varies; removes chlorine, some contaminants. |
| Removes Minerals? | Yes, completely. | Yes, effectively removes most. | Yes, specifically mineral ions. | Often leaves healthy minerals intact. |
| Removes Microbes? | Yes, effectively. | Yes, effectively. | No, not reliably without additional steps. | Removes some, but not all pathogens. |
| Removes Chemicals? | Yes, effectively. | Yes, effectively removes most. | No, not reliably for uncharged organics. | Yes, removes certain chemicals like chlorine. |
| Drinking Suitability | Not recommended for long-term health. | Safe for drinking; can be remineralized. | Not suitable for drinking; absorbs CO2. | Safe in regulated areas; taste improvement. |
Which Water Should You Drink?
For most people in areas with regulated and safe public water supplies, drinking filtered tap water is a cost-effective and healthy choice. Filters, such as activated carbon pitchers or faucet-mounts, can remove unpleasant tastes and odors while leaving beneficial minerals intact. If your tap water quality is questionable, or you want a higher level of purification, a reverse osmosis system is a strong option, especially those that incorporate a remineralization stage. For specific applications where mineral-free water is required, like in medical equipment or humidifiers, distilled water is the appropriate choice, but it is not a suitable primary source of hydration.
Conclusion: Purity vs. Health
While distilled water is the scientifically purest form of water, it is not the ideal choice for everyday drinking due to the complete removal of essential minerals. The best choice for healthy drinking water balances purity with mineral content. Options like properly filtered tap water or remineralized reverse osmosis water provide a high degree of contaminant removal while retaining the beneficial minerals that our bodies need for optimal health. Ultimately, the quest for the purest water should be balanced with the need for water that is both safe and beneficial for your body.
For more information on different types of bottled water and purification methods, consider visiting the International Bottled Water Association (IBWA) website.
Frequently Asked Questions (FAQs)
Is distilled water safe to drink for extended periods?
No, long-term consumption of distilled water is not recommended for drinking. The distillation process removes all minerals, including electrolytes like calcium and magnesium, which are necessary for your health.
Does reverse osmosis remove beneficial minerals?
Yes, reverse osmosis is highly effective at removing total dissolved solids, which include both harmful contaminants and beneficial minerals. However, many modern home RO systems include a remineralization stage to add these back in.
What are total dissolved solids (TDS) and why do they matter?
TDS refers to the total amount of mobile charged ions, including minerals, salts, and metals, dissolved in a given volume of water. While high TDS can indicate contamination, a complete absence of TDS, as in distilled water, means a lack of healthy minerals, giving the water a flat taste.
Is rainwater the purest form of natural water?
Rainwater is the purest form of naturally occurring water, as it is produced through natural distillation (evaporation and condensation). However, as it falls, it can pick up atmospheric pollutants, so it is not pure by the time it reaches the ground.
What is the difference between purified water and distilled water?
Distilled water is a specific type of purified water produced solely by boiling and condensation. Purified water is a broader term for any water treated to remove contaminants, which can be achieved through various methods, including reverse osmosis and deionization.
Does boiling water make it pure?
Boiling water kills most disease-causing microorganisms, making it microbiologically safe to drink. However, it does not remove chemical pollutants, heavy metals, or dissolved salts, which remain in the water after boiling.
Which type of water is best for making coffee or tea?
Many coffee and tea enthusiasts argue that water with some mineral content produces the best flavor. Distilled water, with its lack of minerals, can create a flat-tasting brew, while water that has been filtered to remove chlorine but retain minerals is often preferred.
