According to the Safe Drinking Water Foundation, “TDS stands for total dissolved solids, and represents the total concentration of dissolved substances in water.” Some common inorganic salts (specifically cations: positively charged ions) that exist in water include magnesium, potassium, sodium, calcium, iron, copper, and zinc. Common anions (negatively charged ions) include carbonate, sulfate, and nitrate (WHO). But, how is it that water collects these minerals? Water picks up impurities from natural and man-made sources due to water’s effectiveness as a solvent; some examples include carbonate or salt deposits, mineral springs, sewage, urban and agricultural run-off, wastewater, and salt used to de-ice roads (Drinking Water Extension).
Why is TDS measured? The total dissolved solids in water are evaluated to provide a quantitative amount of dissolved ions in the water. While an indicator test may provide the amount of dissolved ions in the water, it does not provide information on specific ions. A low vs a high concentration of TDS has shown to affect the taste of water. High concentrations of TDS show qualities of a bitter, salty, or brackish taste. Some water connoisseurs describe high concentrations of TDS in water as a prominent “mouthfeel”–a chalky or an abrasive mouthfeel (APEC Water). On the other hand, low concentrations of TDS can give water a flat taste (airy or light mouthfeel). The brackish or salty taste may be from the sodium chloride and potassium chloride present in the water. Additionally, high TDS levels are responsible for increasing the corrosiveness of the water. Thus, in some occasions, high TDS can be responsible for leaving spots on dishes and mineral buildup on pipes or faucets (Safe Drinking Water Foundation). Moreover, varying concentrations of TDS correlate with terms such as hard water and soft water: hard water is associated with higher mineral content with ions such as calcium and magnesium while soft water contains low concentrations of ions.
Usually, high levels of TDS does not always indicate a health hazard. As shown below, while the chart does indicate ratings for levels of TDS (milligrams per litre) from unacceptable to excellent, the ratings conclude the preferred level of TDS in water. “Excellent quality water” has a TDS of 300 or less but the range can be fewer than 30 mg/litre to as much as 6000 mg/litre (WHO). Recommendations are made for aesthetic or technical purposes, but there is little information published about the dangers of consuming low levels of TDS (WQA). (It is important to take into account that while there were early studies relating high TDS on human health, there is no recent data on health effects associated with the ingestion of TDS in drinking-water (Canada.ca)). In the United States, the Environmental Protection Agency (EPA) includes TDS as a voluntary guideline as TDS and other aesthetic substances as a secondary standard: do not pose as great a health risk as primary contaminants.
How does this change the way people see water? For the most part, TDS has an important aspect with respect to palatability, but it is important to understand that TDS itself does not indicate that the water presents as a health risk (Drinking Water Extension). Rather, if elevated TDS is detected, a specific analysis of the present ions and their concentration may provide more information about health risks. Furthermore, to ensure the safety of the water people consume in their private households, it is important for people to periodically test their water for any contaminants, bacteria, pH levels, TDS, and more.
Source of chart: https://www.safewater.org/fact-sheets-1/2017/1/23/tds-and-ph
Source of Information used to create the chart: Concentrations; http://www.who.int/water_sanitation_health/dwq/chemicals/tds.pdf
Direct links to sources:
Comments