Do I need a water softener?

It comes down to one number that your water company already publishes: the hardness of the water at your address, in milligrams of calcium carbonate per litre. Above 200, a softener is a sound purchase for almost any home that owns its plumbing. Below 120, it is money spent on a problem you do not have. In between, your kettle and your patience decide. Here is how to read the number, and how to get yours.

Reading the number

Soft0–60 mg/L

No softener. Scale is not a feature of your life. Enjoy the lather.

Moderately soft60–120 mg/L

No softener. You may see a faint ring in the kettle after a year.

Slightly hard120–180 mg/L

Probably not. Descale the kettle and shower head twice a year and you are done.

Hard180–200 mg/L

A judgement call. Scale is visible and a softener will help, but the payback is slow. Consider one if the boiler is new and you plan to stay.

Very hard200–400+ mg/L

Yes, if you own the house and have a drain. This is where scale costs real money in boiler efficiency, appliance life and cleaning, and a softener pays for itself.

Some water companies report in Clark degrees or French degrees instead. One Clark degree is about 14.3 mg/L, one French degree is 10 mg/L; 200 mg/L is roughly 14 Clark or 20 French.

What hard water looks like in a house

If you have not looked up the number, the house has probably already told you. Count how many of these you recognise.

• White crust on taps, shower screens and around the sink

  Scale deposited where water evaporates. The classic sign; visible from about 150 mg/L.

• A furred kettle element within weeks of descaling

  Heat drives carbonate out of solution. Fast furring means very hard water, usually 250 mg/L and up.

• Soap that will not lather and leaves a film

  Calcium reacts with soap to form scum rather than foam. You are using more of every product.

• Cloudy glasses and a chalky dishwasher

  Scale on glass and on the machine's element. The rinse-aid setting is fighting your water.

• Shower head that needs vinegar every few months

  Scale closing the nozzles. Expect the same inside the pipes you cannot see.

• A boiler that has grown noisier, or a repair bill for the heat exchanger

  The expensive symptom. Scale insulates the element and the boiler works harder for the same hot water.

• Stiff towels and dull, tangled hair

  Minerals left in the fibres. Often blamed on the washing powder; the water is the problem.

Three or more, and you are almost certainly above 200 mg/L. One or two could be moderate water, an old kettle, or the chlorine that every UK supply carries. For skin and hair specifically, a shower filter addresses the chlorine half of the problem without touching the plumbing.

When the answer is no

• Your water is under 120 mg/L. There is no scale to prevent. Most of Scotland, Wales, Cornwall, the Lake District and the Pennines live here.
• You rent, or cannot get to the mains and a drain. A softener is a permanent installation. See the salt-free guide for what is realistic instead.
• Your only complaint is the taste of the drinking water. Hardness is not a taste problem; chlorine usually is. A filter jug is the answer, not a softener.
• You are moving within a year or two. The payback runs over several years. Descale and leave the decision to the next owner.

When the answer is yes

You own the house, the water is 200 mg/L or more, there is a drain within reach of the stop tap, and you are staying. That describes a great many homes across the South East, East Anglia and the Midlands, and for them the question is not whether but which. The next steps are which softener, what it costs and how it is fitted. Or skip the reading and ask installers to come and size one.

Frequently asked questions

Related

• Water hardness checker by postcode
• UK water hardness map by region
• Water and eczema