Hard water and your appliances

If you have lived in this part of the country for any length of time you already know about the kettle. What most people don't realise is that the same process is happening inside the washing machine, the dishwasher, the washer dryer and the coffee machine — just where you can't see it.

Water hardness across our coverage area runs roughly 270–335 mg/l of calcium carbonate. Anything above 200 mg/l is classed as hard; above 300 is very hard. Cambridge Water's own published figures put most of the city and the surrounding villages between 268 and 334 mg/l depending on the supply zone, and Affinity Water's Hertfordshire zones are comparable.

What scale actually does

Calcium carbonate comes out of solution when water is heated. It deposits on the hottest surface available, which in a washing machine or dishwasher is the heating element. A scaled element is an insulated element: it has to run hotter and for longer to bring the water up to temperature, drawing more current and eventually failing — often taking the control board's relay with it.

Elsewhere in the machine, scale narrows the bore of hoses, silts up the pressure chamber that tells the machine how much water it has taken on, stiffens the rubber diaphragm inside solenoid valves, and roughens the impeller housing in the drain pump. Every one of those is a job we attend regularly, and every one is accelerated by our water.

How to tell how bad yours is

You do not need a test kit. Three things give it away, and all three are visible in most kitchens in this region.

• The kettle. If a rinsed, empty kettle has a rough white or grey crust on the element or the base, that same crust is forming in the washing machine and the dishwasher. The kettle is simply the only one you can see inside.
• The shower screen and taps. White spotting that comes back within a day of cleaning is calcium, not soap.
• Lather. If soap and shampoo take a lot of work to foam and leave a film on the bath, the water is hard. Soap reacts with the calcium instead of lathering, and the grey residue is the product of that reaction.

What it costs you

Scale is not only a repair problem, it is a running-cost problem. A heating element with a millimetre of scale on it has to work measurably harder to reach the same temperature, and that inefficiency runs on every cycle for the life of the machine. Independent testing has repeatedly put the energy penalty of a scaled element in the region of a tenth of the machine's heating energy per millimetre of deposit — and heating the water is by far the largest part of what a washing machine or dishwasher costs to run.

The bigger cost is the shortened life. In soft-water parts of the country a decent washing machine element will outlast the machine. Here, elements are a routine replacement, and by the time one fails it has usually been running hot for months and has taken a toll on the components around it.

Which appliances suffer, and how

What actually works

• Descale every eight to twelve weeks. An empty 60°C wash with a proprietary descaler, 500 ml white vinegar or 150 g citric acid. This is the single highest-value thing you can do.
• Keep dishwasher salt topped up. The built-in softener is the only defence the element has. "All-in-one" tablets are not a substitute in water this hard.
• Use the right detergent dose. Hard water needs more detergent, not less — but overdosing leaves residue. Follow the hard-water column on the box.
• Wash hot occasionally. A 60°C cycle once a fortnight clears the biofilm that cool eco washes leave behind.
• Consider a scale inhibitor. An in-line inhibitor on the machine's fill hose is inexpensive and genuinely helps in the hardest zones.
• Leave the door ajar. Nothing to do with scale, but it costs nothing: a washing machine door left open between washes dries the seal, and a dry seal does not grow the black mould that hard-water households see most.

What does not work

Worth saying plainly, because all three are widely sold on the strength of hard-water anxiety.

• Magnetic and electronic "descalers" clamped to the pipe. There is no credible evidence they prevent scale forming on a heating element. They do not remove calcium from the water; nothing that leaves the mineral in the water can.
• All-in-one dishwasher tablets instead of salt. The softening agent in a tablet is real but small, and it is designed for moderately hard water. At 300 mg/l it is not enough, and the machine's own softener — which needs salt — is doing the actual work.
• Doing nothing because the machine is new. Scale accumulates from the first wash. A three-year-old machine in this region that has never been descaled already has a measurable deposit.

If you want to fix it properly

A plumbed-in water softener is the only thing that removes the hardness rather than managing it, and in this region it genuinely changes how long appliances last. It is a real expense and a plumbing job, so it is not for everyone — but for a household that has replaced more than one appliance early, the arithmetic is closer than people expect. We do not sell or fit them and have nothing to gain from saying so.

Short of that, descaling every eight to twelve weeks and keeping the dishwasher salt topped up will get you most of the benefit for the cost of a few pounds a year.

Water hardness where you live

Figures below are from the water companies' own published zone data where available, and from regional geology where a specific zone report isn't published.