What Are Total Dissolved Solids (TDS)?
Total Dissolved Solids, or TDS, is a measurement of all inorganic and organic substances dissolved in a liquid. For water, this includes a mix of minerals, salts, and small amounts of organic matter. These dissolved substances come from a variety of natural and artificial sources, such as water flowing over rocks and soil, agricultural runoff, and even chemicals used in water treatment.
A TDS meter estimates the TDS level by measuring the electrical conductivity (EC) of the water, as dissolved inorganic substances, like salts, metals, and minerals, conduct electricity. The reading is most commonly expressed in parts per million (ppm), which is equivalent to milligrams per liter (mg/L). A higher TDS reading indicates a greater concentration of dissolved solids, while a low reading suggests a purer water sample, as seen with distilled or reverse osmosis (RO) water.
The Direct Link: How Minerals Increase TDS
When you add minerals to water, they dissolve into ions, and these ions are precisely what a TDS meter is designed to detect. This makes the relationship between adding minerals and increasing TDS straightforward. A remineralization filter, for example, is specifically designed to add beneficial minerals back into purified water, which, by its very function, raises the TDS reading. In fact, if you test the TDS of water before and after it passes through a remineralization cartridge, you will see a clear increase.
Some common minerals that contribute to TDS when dissolved in water include:
- Calcium (Ca²⁺): Crucial for bone health and muscle function.
- Magnesium (Mg²⁺): Essential for over 300 bodily processes.
- Potassium (K⁺): Important for nerve and muscle function.
- Sodium (Na⁺): Plays a vital role in balancing bodily fluids.
It's important to understand that a high TDS reading doesn't automatically mean the water is unsafe. The composition of the dissolved solids is far more critical than the total amount. For instance, water with high levels of beneficial calcium and magnesium will have a high TDS but is perfectly safe, while water with a high concentration of harmful heavy metals will also have a high TDS but poses a health risk.
Methods for Adding Minerals to Water
There are several ways to remineralize water, especially after it has been stripped of its mineral content by a purification process like reverse osmosis. These methods offer control over the mineral content and can improve the taste and nutritional profile of the water.
Remineralization Filters
These are post-filters added to reverse osmosis (RO) systems. After the RO membrane removes nearly all dissolved solids, the water passes through this cartridge, which contains a blend of minerals, typically calcium carbonate and magnesium oxide. This process releases a controlled and steady amount of minerals back into the purified water, ensuring a palatable taste and balanced pH.
Concentrated Mineral Drops
Available from various brands, these drops are concentrated mineral solutions that can be added to a glass or bottle of purified water. This method offers a high degree of control over the final TDS and taste, allowing users to customize their water. However, it requires manual addition for every portion of water, unlike a filter cartridge.
Mineral Stones or Cartridges
Some systems use mineral stones or balls made from volcanic rock or other mineral-rich materials. These can be placed in a water dispenser or carafe, where they slowly release minerals into the water over time. The rate of dissolution can vary, making the final TDS less consistent than with a remineralization filter.
Remineralized Water vs. Demineralized Water
Remineralizing water is a process of restoration, adding beneficial elements back into water that has been purified. This stands in stark contrast to water that remains demineralized, such as pure RO or distilled water. The following table highlights the key differences between these water types.
| Feature | Demineralized (RO/Distilled) Water | Remineralized RO Water |
|---|---|---|
| Typical TDS Range | 0–50 ppm | 50–150 ppm |
| Mineral Content | Very low to none | Contains essential minerals like calcium and magnesium |
| Taste Profile | Often described as flat, insipid, or lacking flavor | Enhanced, clean, and refreshing taste due to balanced minerals |
| Hydration Potential | May lead to thirst dissatisfaction and reduced intake | Better hydration, electrolytes aid in quenching thirst |
| pH Level | Slightly acidic, typically 6.0–6.5 | Balanced to slightly alkaline, typically 7.5–8.0 |
| Appliances/Pipes | Less scale buildup, but can be corrosive to metal pipes over time | Generally neutral, helps prevent corrosiveness from pure water |
| Purpose | Suitable for devices that need pure water (e.g., irons, CPAP machines) | Ideal for drinking, cooking, and ensuring mineral intake |
The Verdict: Context is Key
While the answer to "Does adding minerals increase TDS?" is definitively yes, the practical implications depend entirely on the context. For water that has been stripped of its natural mineral content by a filtration process like reverse osmosis, remineralization is a beneficial step. It restores important minerals, improves the taste, and adjusts the pH to a more natural and palatable level. The modest increase in TDS from remineralization does not indicate a problem; rather, it indicates a desirable restoration of healthy components.
However, it's a different story if the source water is already high in TDS due to potential harmful contaminants or excess salts. In that case, adding more minerals without prior purification is not a solution and may not be beneficial. The most important takeaway is that while a TDS meter provides a useful measurement, it does not reveal the composition of the dissolved solids. A comprehensive water test is necessary to understand the full picture of your water quality.
Ultimately, for those seeking to enhance the quality of their purified drinking water, the process of remineralization is a worthwhile consideration. It's a simple, effective way to turn tasteless, demineralized water into a refreshing and healthier beverage. For more information on water quality and standards, consult resources from authoritative organizations like the World Health Organization.
Conclusion: Making an Informed Choice
In summary, adding minerals to water undoubtedly raises its TDS level. This is a direct consequence of the minerals dissolving and increasing the total concentration of solids detected by a TDS meter. For water that has undergone aggressive filtration, such as reverse osmosis, remineralization serves a beneficial purpose: improving taste, restoring essential electrolytes, and balancing the water's pH. The resulting higher TDS is not a sign of impurity but rather of improved quality and palatability. For any water source, however, it is the type of dissolved solids—not just the quantity—that determines its true quality. A balanced, mineral-rich TDS level is a sign of healthy, refreshing water.
