What is water hardness and why does it matter

What is water hardness

Water hardness refers to the concentration of dissolved minerals, specifically calcium and magnesium, in water. These minerals can be naturally occurring or come from sources such as agricultural and industrial runoff. Hard water can have a variety of effects, including making it difficult to lather soap, leaving mineral buildup on fixtures and appliances, and potentially impacting the taste of drinking water.

One of the main ways water hardness arises is through weathering of rock and soil. As water flows over and through rock and soil, it dissolves minerals and carries them into nearby water sources, this is why hardness is different in different areas of the UK. The specific minerals that contribute to water hardness can vary depending on the local geology. For example, areas with limestone and dolomite deposits tend to have harder water.

How is hardness measured

The level of water hardness is typically measured in units of milligrams per liter (mg/L) or parts per million (ppm). Water is considered “soft” if it has less than 17 mg/L of hardness, “moderately hard” if it falls between 60 and 120 mg/L, and “hard” if it has more than 120 mg/L.

The effects of hardness

While hard water is not necessarily harmful to human health, it can present challenges for certain applications. For example, in industrial settings, hard water can cause scaling and corrosion in boilers and cooling towers. In households, it can lead to buildup in pipes and appliances, reducing their efficiency and lifespan. Hard water can also make it difficult to lather soap and shampoo, leaving hair and skin feeling dry and itchy.

Mitigating water hardness

To mitigate the effects of hard water, one common solution is to install a water softener. These devices use ion exchange to remove calcium and magnesium ions from the water and replace them with sodium ions. This effectively “softens” the water by reducing the level of hardness. Another solution is to use water with a reverse osmosis filter, which removes dissolved minerals and impurities from water.

It is important to note that, when attempting to soften hard water, that it can also remove beneficial minerals from water. Therefore, it is crucial to consult with experts and test the water in order to determine the best course of action.


Overall, water hardness is a complex issue that can vary greatly depending on location and water source. Understanding the causes and effects of water hardness, as well as the available solutions, is crucial for maintaining both household and industrial water systems. By researching the specific water hardness issues in different geographical areas, one can make an informed decision on how best to ensure access to safe, clean, and palatable water

24th February 2023
Tom McNamara


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