How do I stop hard water damaging my appliances?

Hard water is dissolved calcium and magnesium, and it is harmless to drink. The problem is what happens when it is heated: the minerals come out of solution and deposit on the hottest surface available, which is the heating element. Scale is an insulator, so the element has to run hotter to deliver the same heat, and it eventually fails. That single mechanism explains why appliance life differs so markedly between hard and soft water areas in the UK, and why a warranty will not cover it — scale is excluded from essentially every appliance warranty on the basis that it is a maintenance matter.

What you'll need

• Your water hardness figure, from the water company's website by postcode
• Dishwasher salt, if you are in a hard water area
• A proprietary descaler or white vinegar or citric acid
• Test strips, to confirm your hardness at the tap (optional)

Step by step

1. Find out how hard your water actually is.Your water company publishes hardness by postcode. Broadly, below about 100mg/l as calcium carbonate is soft and none of this is urgent; above about 200mg/l is hard and all of it matters. Much of the south and east of England is hard; much of the north and west is soft.
2. Set the dishwasher's water softener to your hardness and keep the salt topped up.Almost every dishwasher has a built-in softener with its own salt reservoir in the base, and a hardness setting in the menu that most people never touch. Set it to your actual figure and keep the reservoir full. In a hard water area this is not optional — without it, scale builds on the element and cloudy glassware is the first visible symptom.
3. Do not confuse dishwasher salt with anything else.It is coarse, pure sodium chloride designed to regenerate the resin in the machine's softener. Table salt contains anti-caking agents that clog the resin, and combined tablets containing salt are not a substitute for the reservoir in a genuinely hard area regardless of what the box says.
4. Run a descaling cycle in the washing machine and dishwasher regularly.Every two to three months in a hard water area, on the hottest cycle with a proprietary descaler or with citric acid. It removes scale from the element and the drum before it becomes a hard deposit. It also deals with the detergent residue and biofilm that cause smells, so it is two jobs at once.
5. Descale the kettle when you first see deposit, not when it is thick.White vinegar or citric acid, left to work rather than scrubbed, then rinsed thoroughly and boiled and discarded once. A kettle in a hard area may need it monthly. Thick scale takes several treatments and holds the element hotter in the meantime.
6. Descale the coffee machine and the steam iron on their own schedules.Both have narrow passages that scale blocks completely rather than just insulating, and both usually have a manufacturer-specified descaling product and interval. A scaled espresso machine loses pressure and temperature stability; a scaled iron spits white deposit onto clothes.
7. Soak the shower head and tap aerators.Unscrew and soak in vinegar or descaler, or tie a bag of it over a fixed head. Scale in a shower head reduces flow and redirects jets, and in a tap aerator it produces the spray that goes everywhere. Both are quick and both come back, so make it a routine.
8. Wipe glass and steel dry rather than letting it evaporate.Marks form because water evaporates and leaves the minerals behind. A squeegee on a shower screen and a cloth on taps prevents the deposit rather than removing it later, and it is by far the least effort.
9. Fit a scale inhibitor on the boiler feed if you have a combi.An in-line cartridge or a magnetic inhibitor on the cold feed to the boiler is relatively cheap and protects the appliance that would be most expensive to lose. It is not a substitute for a softener and it does not soften the water, but for the boiler alone it is a reasonable measure.
10. Consider a full softener if the whole house is affected.A softener protects the boiler, cylinder, showers, washing machine and dishwasher together, and cuts detergent use noticeably. It is a significant purchase with an ongoing salt cost and a plumbing requirement, and it is only worth considering above a genuine hardness threshold.
11. Be sceptical of magnetic and electronic scale devices.The evidence for these is much weaker and inconsistent, and they do not remove hardness minerals from the water. If you want the effect of a softener, the honest answer is to buy a softener.
12. Use less detergent, not more, once water is softened.Hard water needs more detergent because the minerals bind it. If you fit a softener or your area is soft, the same dose is now an overdose, which leaves residue in fabrics and in the machine. Reduce it deliberately.

Tips

• Citric acid bought in bulk is much cheaper than branded descaler and is the same active ingredient for most purposes. Check the appliance manual first, as a few manufacturers specify their own product.
• The dishwasher hardness setting is the single most overlooked appliance setting in Britain. Check yours — the default is usually not your area's figure.
• Cloudy glassware coming out of the dishwasher is the early warning that the salt has run out or the setting is wrong. Act on it before the element scales.
• Warranties exclude limescale damage almost universally, which makes descaling a maintenance obligation rather than a nicety in a hard water area.

Common mistakes

• Not using dishwasher salt because the tablets say all-in-one — Combined tablets include a softening agent adequate for moderate hardness only. In a genuinely hard area the machine's own softener still needs salt, and without it the element scales.
• Using table salt in the dishwasher reservoir — Anti-caking agents in table salt clog the softener resin, which is the opposite of the intended effect and can be expensive to put right.
• Waiting until scale is visible before descaling — By the time it is thick on a kettle element it is also on surfaces you cannot see, and it takes several treatments. Descaling on a schedule is much less work than descaling on a symptom.
• Expecting a magnetic device to do what a softener does — It does not remove hardness minerals. The evidence is weak and inconsistent, and the money is better spent on descaling routines or on an actual softener.

Keeping on top of it

• Top up dishwasher salt and check the hardness setting (monthly in a hard area)
• Descaling cycle in the washing machine and dishwasher (every 2 to 3 months)
• Descale the kettle (monthly in a hard area)
• Soak the shower head and tap aerators (every 2 to 3 months)
• Descale the coffee machine and steam iron (per the manufacturer's schedule)

Questions people ask