Should I get a water softener?

Hard water is dissolved calcium and magnesium. It is harmless to drink and quite good for you, and destructive to anything that heats water. A softener exchanges those minerals for sodium, which is why it is a plumbing decision rather than a health one.

What you'll need

• Your water hardness figure from the supplier's website
• Space near the incoming main
• A drain connection nearby

Step by step

1. Find out how hard your water actually is.Your water company publishes hardness by postcode. Below about 100mg/l calcium carbonate is soft and a softener is not worth considering; above about 200mg/l is hard and it is.
2. Look at the evidence in your own house.Scale on the kettle element within weeks, white deposits on taps and shower screens, soap that will not lather, and a scaled shower head are all direct indicators.
3. Understand what it protects.The boiler's heat exchanger, the hot cylinder, the immersion heater, the shower valves, the washing machine and dishwasher elements, and every hot tap. That is where the money is.
4. Understand what it does not do.It does not filter, purify or improve taste. It does not remove existing scale quickly. It does not soften the cold drinking tap, which is deliberately left hard.
5. Keep one hard drinking tap.A softener adds sodium in exchange for calcium. The kitchen cold tap should be plumbed before the softener so drinking and cooking water remains unsoftened.
6. Check you have the space and the drain.Most units live under a kitchen sink or in a utility room near the incoming main, and need a drain connection for regeneration and an electrical socket for the timer.
7. Weigh the running cost.Salt is the main consumable, plus a modest amount of water used in regeneration. It is not large, but it is ongoing and should be part of the comparison.
8. Compare the alternatives honestly.Scale inhibitors that treat the water electrically or magnetically have much weaker evidence behind them. A cartridge inhibitor on the boiler feed is cheap and protects the boiler alone.
9. Think about who lives in the house.Anyone on a medically restricted sodium diet should use the hard drinking tap. Softened water is generally not recommended for making up infant formula.
10. Have it fitted properly.It cuts into the incoming main and needs a bypass so the house has water when the unit is serviced. Most people have it installed rather than fitting it themselves.
11. Expect gradual results.Existing scale dissolves slowly over months as softened water passes over it. Do not judge it in the first fortnight.

Tips

• Check your postcode's hardness figure before anything else. It settles the question in most cases.
• Insist on a hard drinking tap at the kitchen sink. It should be a standard part of any installation.
• Descale the existing shower head and kettle when the softener goes in — the softener will not clear years of deposit quickly.

Common mistakes

• Softening the drinking water supply — Softening exchanges calcium for sodium. The kitchen cold tap should be taken off before the softener so drinking and cooking water is unaffected, which matters for anyone on a low-sodium diet and for infant feeds.
• Buying a magnetic or electronic scale device expecting the same result — The evidence for these is much weaker and inconsistent. They do not remove hardness minerals; a softener does. If you want the effect of a softener, buy a softener.

Alternatives

• Cartridge scale inhibitor on the boiler feed: A small in-line unit that dose-feeds a scale inhibitor into the cold supply to the boiler. Cheap, protects the most expensive appliance, does nothing for the rest of the house.
• Regular descaling: Descaling the kettle, shower head and taps periodically. Free apart from the descaler, but it does nothing for the boiler or the appliances.
• Point-of-use filters: Improve taste and remove chlorine at one tap. They do not soften and they do not protect anything downstream.

Questions people ask