Your Cart is Empty
Celebrate the Bristol Coffee Festival 2026 with Wilfa UK - Get 26% OFF your order with code BCF26!
A cup of filter coffee is around 98.5% water. It's the largest ingredient by a very long way, and it's the one nobody thinks about — we'll happily pay £12 for a bag of beans and then brew it with whatever comes out of the tap.
Water hardness changes both how your coffee tastes and how quickly your machine scales up. Hard water — most of London, the South East and East Anglia — dulls acidity and makes coffee taste flat and chalky, and it means descaling every four to eight weeks rather than every three months. Filtered water helps with both.
Hardness is a measure of dissolved calcium and magnesium. Rain falling on chalk and limestone picks both up on its way through the ground; rain falling on granite picks up very little. That geology is why hardness varies so sharply across the UK.
| Water | Roughly where | What you'll notice |
|---|---|---|
| Soft | Scotland, Wales, the North West, Cornwall and Devon | Soap lathers easily, no kettle scale |
| Moderately hard | Much of the Midlands, the North East, central England | Some scale over time |
| Hard to very hard | London, the South East, East Anglia, Lincolnshire | Chalky kettle, scum on tea, white marks on taps |
Your water supplier publishes a hardness figure for your postcode, which is the accurate answer. The quick answer is your kettle: a chalky white film inside it means you're in hard water territory, and your coffee maker is collecting exactly the same thing.
Here's the part that isn't obvious. Some minerals in water are genuinely useful — they help pull flavour compounds out of the coffee. Distilled or fully softened water makes notably flat, hollow coffee, which surprises people who assume purer must be better.
The problem is quantity. Too much calcium and magnesium and two things happen:
The practical test: if you've bought a light, fruity single origin that was described as bright and it tastes like nothing much in your kitchen, brew one pot with bottled or filtered water and compare. It's a fifteen-minute experiment and the difference is usually not subtle.
This part is less debatable. Every time the machine heats water, some of that calcium and magnesium comes out of solution and stays behind as limescale on the heating element and inside the flow path.
Wilfa machines are built to hold water between 92 and 96°C, and that range is what they're ECBC certified against. Scale insulates the element, so a scaled-up machine delivers water below that range — and under-extracted coffee tastes thin and sour no matter how good the beans are.
Left longer, it stops being about flavour. The most common fault Wilfa is asked about is a machine that has stopped pumping water, and the cause is almost always a flow path narrowed by scale.
Wilfa's guidance is a minimum of every three months. In hard water, treat that as a floor:
| Your water | Descale every |
|---|---|
| Soft | 3 months |
| Moderately hard | 2–3 months |
| Hard to very hard | 4–8 weeks |
Brewing more than once a day shortens all of these. Brewfresh Universal Descaler is £9.60, and the full method takes about fifteen minutes.
It's also worth knowing that damage caused by scale, where descaling hasn't been done as instructed, is excluded from the five-year warranty. In a hard water area that exclusion is a real risk rather than a theoretical one.
Domestic water softeners of the ion-exchange type swap calcium for sodium. Excellent for your pipes and your washing machine, not ideal for coffee — very soft, sodium-rich water makes flat, slightly salty-tasting brews. If you have a softener, use the unsoftened drinking tap for the coffee maker.
Does hard water affect the taste of coffee?
Yes. Hard water buffers some of the acids that give coffee its brightness and fruit character, so the cup tastes flatter and duller. Beyond a certain hardness you can also taste the minerals themselves as a chalky, drying quality.
Should I use filtered water in my coffee maker?
In a hard water area, yes. A jug filter improves taste and slows limescale build-up in the machine. It doesn't remove the need to descale, but it extends the interval between descales.
How often should I descale in a hard water area?
Every four to eight weeks, rather than the three-month minimum Wilfa recommends generally. Brewing more than once a day shortens that further.
Is distilled or very soft water better for coffee?
No. Some dissolved minerals actually help extract flavour from coffee, so distilled or fully softened water produces noticeably flat, hollow-tasting brews. If you have a domestic ion-exchange water softener, use the unsoftened drinking tap for your coffee maker.
How do I know if I have hard water?
Look inside your kettle. A chalky white film means hard water. Your water supplier also publishes a hardness figure for your postcode, which is the accurate answer.
If your coffee has never quite tasted the way it should, and the beans and the dose are right, the water is the next place to look — and it's the one variable most people have never changed.
Shop Brewfresh Descaler · How to descale your machine · Get your dose right
