Throughout the world, a large percentage of the population is drinking water that is classified as hard. The hardness of water is determined by the levels of dissolved magnesium and calcium within the supply. A common misconception regarding hard water, one that has been refuted by the World Health Organization (WHO), is that it can be detrimental to health. The National Research Council goes further by promoting the benefits of hard water, stating that the large quantities of calcium and magnesium can actually contribute to the recommended daily allowance (RDA) of these minerals.
In the United States, nearly 90% of homes have hard water. A similar level is noted in the United Kingdom, where the majority of domestic supplies are considered to be between hard and very hard in terms of water mineral content. Other developed countries generally feature a wide spread of water hardness.
When considering hard water, it should be noted that there are both advantages and disadvantages for home owners through having high mineral-content water fed into their homes. One of the benefits of hard water comes from the ingestion of calcium ions from the water along with magnesium traces. Both of these minerals are essential in the modern diet. Many people also consider hard water to possess a more pleasant taste than soft water.
Another by-product of hard water can be both a benefit and a disadvantage, depending on where in the pipe system it occurs; this is the formation of a hard layer of carbonate within pipes, faucets, and kettles known as lime scale. This carbonate layer is insoluble and can therefore restrict water flows through pipes. Lime scale can also form on the insides of kettles and around faucet heads, although this is not entirely detrimental other than from an aesthetic perspective. As one of the benefits of hard water, lime scale can also extend the operable life of water pipes by keeping the water flow and pipe material separated.
The benefits of hard water are often overshadowed by concerns regarding the safety of drinking high-mineral content water. These concerns stem from research that has suggested a link between male cardiovascular health and the level of calcium present in water. After studying the available evidence and research, the WHO concluded that insufficient data was presented to be able to accurately confirm a link between the two factors. With a large proportion of the developed world’s population being subject to hard water supplies, there would appear to be no convincing evidence to suggest any correlation between water hardness and health issues.