Softening Water

Water softening is the process of removing minerals, notably calcium and magnesium, from hard water.
Hard water is water that contains a high concentration of dissolved minerals.
The presence of these minerals can interfere with the action of soap, leading to the creation of ‘scum’ and ‘scale’ in heating systems and pipes.
The hardness of water can either be temporary or permanent. Temporary hardness can be removed by boiling, while the permanent requires different treatment methods.
Temporary hardness is due to the presence of soluble bicarbonates (of calcium and magnesium). Boiling such water promotes the formation of insoluble carbonates, which can then be easily removed.
Permanent hardness is due to other salts like sulphates and chlorides of calcium and magnesium which don’t turn insoluble or can’t be removed by boiling.
Two major ways to soften hard water are through ion exchange resins and the addition of washing soda.
Ion exchange resin method involves the passing of hard water through an ‘ion exchange column’. The process exchanges calcium and magnesium ions in the water with sodium ions in the column.
The addition of washing soda (sodium carbonate) precipitates the calcium and magnesium ions out of the water as their respective carbonates, thereby softening the water.
Another approach to water softening is using a base exchange system where sodium ions replace the calcium and magnesium ions.
Softening water is an essential process as hard water leads to the accumulation of limestone scale in pipes, which can reduce their efficiency or lead to blockages. In industries, this could lead to significant cost in terms of energy inefficiencies and equipment repair or replacement.
It’s important to note that while soft water is kinder to pipes and makes soap lather better, it can lead to high sodium content in the water, which is not ideal for drinking or for those on sodium-restricted diets.
The presence of certain minerals in hard water also offers some taste and potential health benefits, so total softening isn’t always desirable.
In a conundrum, distilled water, which is pure and lacks all minerals, could be considered the ‘softest’ water - but it is not suitable for drinking due to its lack of beneficial minerals and potential health implications. Consequently, a balance in mineral content is often sought for optimum water quality.
Knowledge of water hardness and softening is indispensable for understanding water treatment processes and for informing choices at both individual and industrial levels.