Is softened water safe (and better) to drink?

Water hardness itself has no known negative health effects. The more useful question, if you're installing a softener, is what softening actually changes about your drinking water, and who should think twice about it.

Hardness itself isn't a safety issue

Hard water is not considered a health risk. If anything, the calcium and magnesium it contains make a small contribution to dietary intake. The differences people notice, taste, the feel of it, how it affects tea or coffee, are matters of preference, not safety.

But softening adds sodium

Ion-exchange softeners work by swapping calcium and magnesium for sodium. As a rough industry figure, softening adds around 46mg of sodium for every 100mg/litre of hardness (as calcium carbonate) removed, so the harder your untreated water, the more sodium ends up in the softened version. UK drinking water regulations cap sodium at 200mg per litre, and properly maintained residential softeners normally stay well under that.

Who should think twice about drinking it

Common guidance is that softened water isn't the right choice for preparing infant formula, and anyone on a medically prescribed low-sodium diet should check with their GP before using it as drinking water. This isn't a reason to avoid a softener altogether. It's a reason to plan for one unsoftened tap in the house.

The practical fix: keep one tap unsoftened

Most professional softener installations include a bypass so at least one cold tap, usually the kitchen sink, or a separate dedicated tap, stays connected to the unsoftened supply, for drinking, cooking and making up baby formula. If you're getting quotes, ask specifically whether this is included.