What is Deionised Water?
Deionised water, also known as demineralised water or DI water, is water that has had most or all of its dissolved mineral ions removed through a process called ion exchange. During this process, water is passed through special resin beads that attract and capture positively charged ions (cations) like calcium, magnesium, and sodium, and negatively charged ions (anions) like sulfates and chlorides. This results in water with extremely low electrical conductivity and a high level of chemical purity, making it suitable for scientific and industrial applications.
Unlike distillation, which removes a broad range of impurities by boiling and condensation, the deionization process does not remove uncharged substances. This critical distinction is one of the key reasons why DI water is not safe for drinking. While it may be chemically 'pure' in the ionic sense, it is far from biologically safe for human consumption.
Health Risks of Drinking Deionised Water
There are several significant health risks associated with drinking deionised water, which is why health authorities do not recommend it for daily hydration.
Mineral Depletion from the Body
Deionised water is often referred to as "hungry" or "aggressive" water because its lack of ions makes it an excellent solvent, actively seeking to absorb minerals from its surroundings. When consumed, this process can pull essential minerals directly from your body's tissues. Over time, continuous consumption can lead to serious mineral deficiencies.
Possible health consequences include:
- Electrolyte Imbalance: Deionised water can leach electrolytes like sodium, potassium, calcium, and magnesium from the intestinal lining. Electrolytes are crucial for nerve function, muscle contractions, and maintaining fluid balance.
- Bone Health Issues: The leaching of calcium and magnesium can affect bone density and increase the risk of fractures.
- Cardiovascular Problems: Long-term studies have shown a link between low-mineral water consumption and an increased risk of cardiovascular disease.
Potential for Biological Contamination
The deionization process effectively removes ions, but it does not remove uncharged contaminants such as viruses, bacteria, and other organic pathogens. If the source water for deionization is not properly pre-filtered or if the system is not sterilized, these microbes can remain in the water and pose a serious health risk.
Corrosive Nature and Toxic Leaching
Because deionised water is so pure and aggressive, it readily attacks and leaches materials from the containers and pipes it comes into contact with. This can introduce toxic substances into the water before it even reaches your glass.
Common sources of toxic leaching include:
- Plumbing: DI water can corrode metal pipes, including copper and lead, releasing these heavy metals into the water.
- Plastic Containers: It can leach plastic monomers and other chemical compounds from storage bottles, especially over time.
- Ion Exchange Resins: There is a possibility that trace amounts of the ion-exchange resin material could be present in the water, which can be toxic.
Comparison: Deionised vs. Tap vs. Distilled Water
To understand the differences and safety implications, it's helpful to compare deionised water with other common water types.
| Feature | Deionised Water | Tap Water | Distilled Water |
|---|---|---|---|
| Purification Method | Ion exchange resin removes charged ions | Municipal treatment (filtration, disinfection) | Boiling and condensing steam removes minerals and most contaminants |
| Mineral Content | Virtually none; extremely low TDS (Total Dissolved Solids) | Contains healthy, naturally-occurring minerals | Virtually none; extremely low TDS |
| Contaminants Removed | Charged mineral ions only; uncharged pathogens remain | Harmful bacteria and contaminants, but may have trace minerals | Minerals, viruses, bacteria, and other impurities |
| Pathogen Risk | High, as bacteria and viruses are not removed | Low, as water is disinfected by municipal systems | Very low, as boiling kills most pathogens |
| Taste | Flat and unpleasant due to lack of minerals | Varies by location and mineral content | Bland, but generally considered safer to drink than DI water |
| Corrosive Nature | Highly corrosive; can leach toxins from containers | Generally non-corrosive due to mineral content | Corrosive; can also leach from containers over time |
Appropriate Uses for Deionised Water
While unsuitable for drinking, deionised water has many essential and appropriate applications where the absence of mineral ions is beneficial.
- Laboratory Experiments: Used as a blank or solvent to prevent minerals from interfering with precise chemical reactions and analysis.
- Cosmetics and Pharmaceuticals: Ensures purity and consistency in manufacturing processes.
- Electronics Manufacturing: Used to prevent mineral deposits that could damage sensitive components.
- Cooling Systems: Prevents mineral buildup (scaling) in industrial machinery and automotive cooling systems.
- Cleaning: Leaves surfaces spotless without mineral residue, making it ideal for window washing and sensitive equipment.
Conclusion
In summary, while the term "pure water" might sound appealing for hydration, it's crucial to understand the scientific reality behind deionised water. Its ionic purity, achieved through ion exchange, is not a measure of its biological safety. The process leaves behind uncharged pathogens, and the water's aggressive, mineral-free nature poses a dual threat: it actively leaches essential minerals from your body and can absorb toxic substances from storage containers. For everyday consumption, a properly filtered water source that retains beneficial minerals is the far healthier and safer option.
For more detailed health information on mineral-poor water, consult the World Health Organization's report on demineralised drinking water.
Why Can't You Drink Deionised Water?
- Leaches Minerals: Deionised water is an aggressive solvent that pulls essential minerals like calcium and magnesium from your body's tissues, potentially leading to long-term deficiencies.
- Retains Contaminants: The ion exchange process does not remove uncharged organic compounds, viruses, or bacteria, which could cause illness if the source water is not pre-treated.
- Corrodes Containers: Its purity makes it corrosive, allowing it to leach toxic metals and chemicals from pipes and plastic storage bottles, which you would then ingest.
- Unpleasant Taste: The absence of minerals gives deionised water a flat, unpalatable taste, which can deter people from proper hydration.
- Not Thirst-Quenching: Lacking the electrolytes found in regular water, deionised water is less effective at satisfying thirst and restoring what is lost through sweat.
- Daily Hydration Risk: While an accidental sip is harmless, relying on deionised water for daily hydration can lead to severe mineral imbalances over time.
- Industrial Use Only: Deionised water is produced for specific industrial, scientific, and manufacturing applications where mineral ions are problematic, not for drinking.
Frequently Asked Questions
Q: What happens if I accidentally drink a small amount of deionised water? A: A small, one-off consumption is unlikely to cause any harm. The risks are associated with long-term, regular consumption, which can lead to mineral depletion and other health issues.
Q: Is deionised water the same as distilled water? A: No, they are purified differently. Distillation involves boiling and condensing vapor, which removes a broader range of impurities including pathogens. Deionization only removes ions.
Q: Why is deionised water used in laboratories if it's potentially contaminated? A: Deionised water is used in labs for its ionic purity, which prevents interference in experiments. For biological applications, further filtration or sterilization is typically used, or distilled water is preferred.
Q: Can I use deionised water for cooking? A: It is not recommended. Cooking with deionised water can leach minerals from the food you are preparing, further contributing to a potential dietary mineral deficiency.
Q: How does deionised water affect my teeth? A: Deionised water lacks minerals like fluoride, which is added to municipal water to prevent tooth decay. Regular consumption could increase the risk of dental problems, especially if it's your primary water source.
Q: Does deionised water purify my body? A: No. This is a common misconception. Instead of purifying your body, its "hungry" nature can cause it to absorb and deplete essential minerals from your body's cells and tissues.
Q: What is a safer alternative to deionised water? A: For safe, everyday hydration, tap water is a perfectly acceptable choice in most developed areas. For enhanced purity, a home filtration system or reverse osmosis system that retains or remineralises the water is a safe and effective alternative.
