What is Total Dissolved Solids (TDS)?
Total Dissolved Solids (TDS) refers to the concentration of inorganic salts and small amounts of organic matter dissolved in water, which can include minerals like calcium, magnesium, and potassium, as well as salts and metals. The level of TDS is measured in parts per million (ppm) or milligrams per liter (mg/L), and it can significantly affect the water's taste, odor, and appearance. A water's TDS is not a direct measure of its safety, but it can indicate the presence of certain substances that influence its overall quality. For example, high TDS can suggest elevated mineral or salt content, while very low TDS might result from extensive purification that removes beneficial minerals along with contaminants.
The Misleading Nature of an "Average" TDS
Due to the vast differences in source water and treatment methods, pinpointing a single average TDS for all bottled water is inaccurate. The TDS of bottled water is not regulated as a health-based standard by the U.S. Environmental Protection Agency (EPA), but rather as a secondary standard based on aesthetic effects like taste and staining. The TDS value is a reflection of the water's source and processing, not a singular metric of its quality. For consumers, understanding the type of bottled water is more useful than seeking an overall average.
TDS Levels by Bottled Water Type
Purified Bottled Water
Purified water is treated through processes like reverse osmosis (RO), distillation, or deionization to remove almost all dissolved solids. This results in a very low TDS level, often below 50 ppm, and sometimes close to zero. Brands like Aquafina and Dasani fall into this category. The aggressive purification process removes beneficial minerals, leaving a 'flat' or neutral taste that some prefer, while others find it less appealing. This type of water is ideal for sensitive equipment like humidifiers and irons, where mineral buildup can cause damage.
Spring and Mineral Bottled Water
Spring water and mineral water come from natural, protected underground sources and, by definition, contain varying levels of naturally occurring minerals. Their TDS levels are not manipulated to be consistently low but instead reflect the unique mineral composition of the geological formation the water passes through. This results in a wide range of TDS values and distinct tastes. Brands like Evian (around 247 ppm) and Fiji (around 132 ppm) have higher TDS levels that contribute to their characteristic mineral-rich flavors. The Fine Water Society categorizes these natural waters based on their TDS, from 'super low' (0-50 mg/L) to 'very high' (over 1,500 mg/L).
Factors Influencing Bottled Water TDS
Several factors contribute to the TDS level found in a bottle of water, from its source to its final treatment:
- Source of Water: Natural spring and mineral waters gain their TDS from minerals dissolved as the water flows through rock formations underground. The geology of the source area heavily influences the final TDS value.
- Purification Process: For purified waters, the treatment method is the most important factor. Techniques like reverse osmosis and distillation are designed to strip water of its dissolved solids, drastically lowering the TDS.
- Mineral Reintroduction: Some producers of purified water add a small amount of minerals back into the water after processing to improve its taste. This process, known as remineralization, results in a slightly higher, though still low, TDS level.
- Runoff and Pollution: While heavily monitored, a water source can be influenced by man-made factors like agricultural runoff and industrial waste, which can alter its TDS.
Bottled Water TDS Comparison Table
| Bottled Water Type | Approximate TDS Range (ppm) | Examples | Taste Profile | Notes |
|---|---|---|---|---|
| Purified | < 50 | Aquafina, Dasani, Smartwater | Neutral, sometimes flat | Treated to remove nearly all minerals; consistent quality |
| Natural Mineral | 50–300+ | Evian, Fiji, San Pellegrino | Mineral-rich, variable | TDS depends on the natural mineral content from the source |
| Spring | 50–200 | Arrowhead, Nestle Pure Life | Crisp, light mineral taste | Contains natural minerals but often a more balanced profile |
Health and Taste: The Role of TDS
The TDS of your bottled water impacts both its taste and potential health benefits. The ideal TDS range for taste, as defined by the WHO, is between 50-300 ppm. Water on the lower end of this spectrum is often described as tasteless or 'flat,' while water with moderate mineral content is typically perceived as crisp and fresh. Higher TDS levels can lead to a more pronounced, sometimes bitter or salty, flavor due to the high mineral concentration.
Regarding health, some minerals found in water, like calcium and magnesium, are beneficial for human health. However, a TDS meter alone does not distinguish between these beneficial minerals and potentially harmful contaminants. While regulatory bodies like the EPA and WHO have guidelines for TDS, these are largely based on aesthetic palatability, not health risks. A high TDS reading might indicate an issue, but further testing is required to identify specific contaminants. Conversely, extremely low TDS water from reverse osmosis or distillation may offer no mineral benefits, so some purifiers re-mineralize the water to improve taste and nutritional value.
How to Measure and Choose Your Bottled Water TDS
To know the TDS of your bottled water, you can check the label, which often lists the mineral content, or use a portable TDS meter for a direct reading. Ultimately, the 'best' TDS is a matter of personal preference and health goals. For everyday hydration, a balanced TDS (50–300 ppm) is often considered ideal. For those who prefer a neutral taste or use water in appliances, a very low-TDS purified water is a better choice. To understand the various regulations on drinking water quality, consult resources like the WHO's documentation on total dissolved solids.
Conclusion
The average TDS of bottled water is not a useful metric because the total dissolved solids content varies dramatically between different water types. Purified waters are designed for a near-zero TDS, offering a neutral taste, while natural spring and mineral waters retain their geological mineral content, leading to a wider range of TDS and unique flavor profiles. Consumers should focus on the type of water they prefer, whether it's the purity of treated water or the taste and mineral benefits of natural sources. Ultimately, consulting the product label is the most reliable way to know the TDS of your bottled water and ensure it aligns with your personal preferences and needs.
Understanding Bottled Water TDS
What is Total Dissolved Solids (TDS)?
TDS refers to the concentration of inorganic salts and small amounts of organic matter dissolved in water, including minerals like calcium, magnesium, and potassium, as well as salts and metals.
Is There a Single Average TDS for Bottled Water?
No, there is no single average TDS for all bottled water due to the wide variation between purified, spring, and natural mineral sources. Purified water has a very low TDS, while natural mineral water has a higher, more variable TDS based on its source.
How Do TDS Levels Differ Between Purified and Mineral Water?
Purified water (like Aquafina) is treated to have a very low TDS (often < 50 ppm), whereas natural mineral water (like Evian) contains naturally occurring minerals, resulting in a higher TDS that varies by brand.
What is a Healthy TDS Level for Drinking Water?
The World Health Organization considers a TDS range of 50-300 mg/L as palatable and optimal for taste and mineral content. However, other guidelines and personal preferences vary.
Does Boiling Water Reduce TDS?
No, boiling water concentrates dissolved solids as some of the water evaporates. It kills microorganisms but does not remove minerals or salts.
How Does TDS Affect the Taste of Bottled Water?
Low TDS water often tastes flat or neutral, while higher TDS levels, found in many natural mineral waters, can give the water a more pronounced, mineral-rich, or sometimes salty flavor.
How Can I Check the TDS of My Bottled Water?
The most reliable way is to check the product label, which often lists the mineral content. You can also use a portable TDS meter for a direct reading of the water's conductivity, which approximates the TDS.
Is Low TDS Water Bad for You?
Water with very low TDS (below 50 ppm), while safe, may lack beneficial minerals like calcium and magnesium. For some, it might not offer the same potential health benefits as water with a balanced mineral content.
Does High TDS Mean Contaminated Water?
Not necessarily. High TDS often simply indicates a high concentration of harmless minerals. However, consistently very high TDS (over 1000 ppm) can signal potential issues and may require further testing for specific contaminants.
Can I Drink Water with 1000+ ppm TDS?
Water with TDS levels above 1000 ppm is generally not recommended for regular consumption, as it can have an unpleasant taste and may indicate excessive salts or other pollutants.
Why Do Some Purified Waters Still Have a Low TDS Reading?
Some manufacturers re-mineralize purified water by adding back a small, controlled amount of beneficial minerals to improve taste and provide some nutritional value. This process results in a slightly higher, but still low, TDS level.
Should I Choose Bottled Water Based on TDS?
Your choice should be based on your personal preferences for taste, your health needs (e.g., mineral intake), and the intended use of the water (e.g., daily hydration, brewing coffee). TDS is just one factor in assessing water quality.
World Health Organization. "Total dissolved solids in Drinking-water." (2003)
