Understanding TDS: What it is and What it Isn't
Total Dissolved Solids (TDS) refers to the concentration of inorganic salts, organic matter, and other substances dissolved in water. These include essential minerals such as calcium, magnesium, and potassium, as well as potential contaminants like lead, arsenic, and nitrates. TDS is measured in parts per million (ppm) or milligrams per liter (mg/L). It is a key indicator of water quality, but it's important to understand that TDS alone does not determine if water is safe to drink. For example, high TDS could simply mean harmless minerals, while low TDS could still contain unseen harmful contaminants that require testing.
The Health Effects of Consuming Low TDS Water
While water with a TDS reading under 50 ppm may seem 'pure,' its extreme lack of minerals can have several unintended consequences for your health over the long term. This is why water purification systems like reverse osmosis (RO), which can produce very low TDS water, often include remineralization stages.
Potential long-term health risks include:
- Mineral Deficiency: Low TDS water lacks essential minerals such as calcium, magnesium, and potassium. Prolonged reliance on demineralized water can contribute to dietary mineral deficiencies, impacting bone health, muscle function, and heart rhythm. Some experts suggest a minimum of 10 mg/L of magnesium and 20 mg/L of calcium is desirable.
- Electrolyte Imbalance: Minerals help maintain the body's electrolyte balance. Water with extremely low TDS does not contribute electrolytes and, in the context of a diet already low in these minerals, could theoretically affect the body's natural balance. Electrolyte imbalance is particularly risky for children and the elderly.
- Leaching of Minerals: Some research suggests that demineralized water is 'aggressive' and can potentially leach minerals from the body, though this is debated and a balanced diet can often compensate. Using this water for cooking can also cause vegetables, meat, and cereals to lose a significant portion of their mineral content during preparation.
- Metabolic and Cardiovascular Issues: Older WHO reports and some studies have linked long-term consumption of demineralized water to metabolic dysfunction, increased urine output, and a higher risk of cardiovascular disease, though more research is needed.
- Corrosion of Pipes: The 'hungry' nature of very low TDS water can cause it to leach metals from plumbing, potentially adding harmful substances like lead and copper to your drinking water from your own home's pipes.
Short-Term Effects and Palatability
Besides the long-term concerns, there are immediate impacts to consider with low TDS water:
- Bland Taste: Water with very low TDS often tastes flat, bland, or even metallic. This is because the flavor of drinking water is influenced by its mineral content. This can discourage adequate water consumption.
- Hydration Efficiency: While still hydrating, some evidence suggests that demineralized water may not be absorbed as effectively, which can affect the body's hydration process.
Comparison of Water TDS Levels
To better understand the differences, here is a comparison of water at different TDS ranges.
| TDS Range (ppm) | Classification | Palatability | Key Characteristics | Potential Risks of Long-Term Use |
|---|---|---|---|---|
| < 50 | Very Low (Demineralized) | Flat, insipid | Lacks essential minerals like calcium and magnesium. | Mineral deficiency, electrolyte imbalance, reduced hydration efficiency. |
| 50–150 | Ideal/Excellent | Clean, pleasant | Excellent balance of purity and beneficial minerals. | Minimal to none, considered optimal for health and taste. |
| 150–300 | Good | Good | Contains healthy minerals, generally palatable. | Minimal, well-within WHO and EPA guidelines for palatability. |
| 300–500 | Fairly Acceptable | Potentially noticeable taste | Within acceptable standards, but flavor may be affected. | Minimal health concerns unless specific harmful contaminants are present. |
| > 500 | High/Not Recommended | Salty, bitter, or metallic taste | May contain excessive minerals or contaminants; requires investigation. | Possible long-term health risks if contaminants are present. |
Achieving the Ideal TDS Level
If you find your drinking water has a TDS below 50, or you want to ensure a healthy balance, there are several steps you can take:
- Test Your Water: Use an inexpensive, handheld TDS meter to get a quick reading. This is especially important for households using RO systems or private well water, as levels can fluctuate.
- Install a Remineralization Filter: Many RO systems can be fitted with a post-filter that adds back beneficial minerals like calcium and magnesium. This is the most effective way to restore optimal TDS levels while maintaining high purity.
- Blend Water Sources: If you have two water sources (e.g., purified and unfiltered), you can blend them to achieve a balanced TDS. Some advanced RO systems have a blending valve for this purpose.
- Add Mineral Drops: For a low-tech solution, you can purchase and add concentrated mineral drops to your drinking water.
- Consider Bottled Water: Some high-quality bottled mineral waters have a balanced TDS and can provide a good alternative, but check the label as some brands also use very low TDS purified water.
Conclusion: The Final Verdict on Low TDS Water
While water with a TDS reading below 50 is microbiologically safe and free of many contaminants, it is not ideal for regular long-term consumption. The absence of essential minerals like calcium and magnesium can lead to deficiencies, electrolyte imbalances, and potentially increase health risks over time, especially if your diet is lacking. A balanced TDS level, typically between 50 and 300 ppm according to health organizations, provides the best mix of purity, palatability, and mineral content for optimal health.
Rather than viewing low TDS as the ultimate sign of purity, consider it a signal to take corrective action. If your water source results in a very low TDS, installing a remineralization filter is a simple and effective way to restore the healthy mineral balance. This ensures you can enjoy truly clean water without sacrificing the vital minerals your body needs to thrive.
For more detailed information on drinking water safety and demineralized water, you can consult the World Health Organization's report on Health Risks from Drinking Demineralised Water.
