Total Dissolved Solids & Water Hardness


Do you know the difference between total dissolved solids (also known as TDS) and water hardness?

As the two are closely related, we were inspired to compare these overlapping aspects of water.

Let’s start with TDS, which is the combined content of all inorganic and organic compounds found in water. When one hears or reads about “total dissolved solids,” this is typically in relation to freshwater with a value equal up 500 parts per million. TDS is considered when analyzing the quality of lakes, rivers and streams, as well as drinking water in general. The total dissolved solids in water supplies originate from natural sources, sewage, urban and agricultural run-off, and industrial wastewater.

For reference, 1 ppm indicates one milligram of dissolved solids per kilogram of water. Of the compounds found in the water, the most common are calcium, phosphates, magnesium, sodium, potassium and chloride, but any ion that is present will contribute to the total.

The organic ions include pollutants, herbicides and hydrocarbons. It is not associated with adverse health effects, although it is used in the process to define the characteristics of drinking water and an indicator of contaminants.

Additionally, there are other types of water in which TDS is classified. This includes brackish water (TDS equal to 500-30,000 ppm), saline water (TDS equal to 30,000-40,000) and hypersaline (TDS is greater than 40,000 ppm). These all include increasing levels of saline, from former to latter.

There are a few ways for one to indicate the levels of total dissolved solids in water. One is the aptly named TDS meter, which indicates the concentration of dissolved solid particles in the water in question. However, one of the most accurate ways to test TDS would be in a laboratory. Here, the water is evaporated, which then leaves behind solutes as residue. From there, the residue is weighed, allowing for an accurate representation of the dissolved solids.

In regard to mineral water specifically, total mineralization is the sum of all minerals in water. In Germany, where Mitte is based, this has been divided into several categories by the German legislature.

This includes low-mineralized (TDS lower than 500 mg/l), very low mineralized (TDS lower than 50 mg/l) and high mineralized (TDS higher than 1500 mg/l).

For water hardness, known to some as total hardness, this is the concentration of dissolved ions of the alkaline earth metals in the water. Hardness is not caused by a single substance but by a variety of dissolved polyvalent metallic ions, predominantly calcium and magnesium cations. This occurs when water passes through deposits of the earth, such as limestone, chalk and other rock, where are largely made up of calcium, magnesium carbonates, bicarbonates and sulfates. Hardness is most commonly expressed as milligrams of calcium carbonate equivalent per liter.

When compared to soft water (which has low levels of ions, particularly calcium and magnesium), hard water proves to be problematic in industrial and domestic settings, where the buildup of limescale in everything from boilers to kettles to plumbing is common. This is a particular problem in the United States of America, in which 85% of homes are supplied with hard water.

Data finds that about half of the water stations in the country have hardness over 120 mg per liter of calcium carbonate equivalent, which ranks the water as “hard” or “very hard.”

While there has been debate regarding the safety of hard vs. soft water, the World Health Organization noted that:

“There does not appear to be any convincing evidence that water hardness causes adverse health effects in humans.”

That’s good news for Americans – but it doesn’t mean that all is perfect.

While hard water is found throughout the entire United States, it’s noted that hard water is particularly common within the bi-national Great Lakes region, in which the five lakes (and various waterways) make up over 20% of the freshwater on the surface of the earth.

In relation to both, hardness does not always result from high TDS. There are many spring or well waters that are high in sodium but naturally soft. Bedrock wells greater than 100 feet deep in sandstone aquifers typically produce soft, sodium-chloride type water with high TDS levels.

Whether TDS, hard water, both, or another type of water entirely, make sure you stay informed about the water you are consuming on a daily basis.

By Mitte Team — Sep 25, 2019
The information contained in this article is provided for educational and informational purposes only, and should not be construed as health or nutritional advice.

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