Many of us will be familiar with hard water from its effects: build-up of limescale in kettles, clogged up pipes, residues in our baths and basins, not to mention its feel on our skin and effect on our hair. British Water estimates that “hard water is supplied to 60% of homes in the UK: especially in central, eastern and southern areas of England”.

But what does it actually mean for water to be ‘hard’? Basically it means that certain dissolved minerals, principally magnesium and calcium, are highly present in the water. Rainwater is naturally ‘soft’, but when it percolates through limestone, chalk, dolomite or other magnesium and calcium-containing rock, it picks up these minerals and becomes ‘hard’. The hardness of the water supplied to your home will depend on where you live in the country, and from where exactly that water is sourced.

When we use hard water in our homes, the dissolved magnesium and calcium precipitate out of it as scale, causing the building and clogging effects we have described above, which subsequently have their expense. Hard water also interferes with the action of cleaning products such as soaps and detergents, reducing their ability to lather – which means more of the product is required to do its job. Because of these effects of hard water, the idea of water softening has increasingly gained a grip on people’s minds, with domestic water-softeners becoming more efficient, available and affordable.


Water softening has actually been around for almost two centuries and can take place at different levels or stages of water-use:

Lime-softening: This generally takes place at a supply or industrial level, before the water reaches our homes, and involves treating hard water with limewater to make the dissolved calcium and magnesium precipitate.

Chelation: This takes place at the level of product manufacture and involves certain ingredients being added to soaps, shampoos and detergents which have a softening effect on the water with which these products are used.

Ion-exchange: This is the process by which most domestic water-softening devices work, and involves calcium and magnesium ions in the water being replaced by sodium ions.

A domestic water-softening device operating by ion exchange is a unit ranging in size from something like bathroom-bin proportions to something like kitchen-bin proportions, which can fit inside a cupboard or under a kitchen worktop and gets connected to the mains water supply, for all the water coming into one’s home to pass through it. One advantage of such a device is that it addresses the problem of hard water at the source, as water enters one’s home, rather than simply addressing the damage caused by hard water with descaling products and the like. British Water also estimates that a water softener will effectively pay for itself within 2–4 years by reducing the need for such products and, in general, protecting bathroom equipment and all water-using appliances.

When considering whether or not to invest in a water-softener as part of your heating and plumbing installation, it is important to be aware of potential disadvantages. Ion-exchange devices which replace calcium and magnesium with sodium raise the quantity of this latter chemical in the water to levels which, while of negligible impact to most, are not necessarily so to people on sodium-restricted diets, to babies or to plants. Water in its unsoftened, ‘hard’ state may also have health benefits deriving from the reduced solubility of certain toxic metal ions in hard water. And while hard water may leave residues on your bath, it more effectively removes soap residues from your skin. Some of these disadvantages can be circumnavigated by retaining an unsoftened-water mains tap alongside the softened-water tap from your device.

(Photos by hyperlux and mrmac04)