Here's something most people don't think about: a cup of coffee is roughly 98% water. The coffee itself is only 2%. So if your water doesn't taste good - or if it's full of minerals that interfere with extraction - it doesn't matter how good your beans are. The coffee will suffer.
Hard water vs. soft water
The UK has a real mix of water hardness depending on where you are. London and the South East are notoriously hard. Scotland, Wales, and the South West tend to be softer. You can check your area on your water company's website.
Hard water contains high levels of calcium and magnesium. In moderation, some mineral content is actually good for coffee - it helps extract flavour. But too much makes coffee taste flat, chalky, or dull, and it can make the body feel heavy and unpleasant.
Very soft water has the opposite problem. Without enough minerals, extraction is poor and coffee can taste thin and sour. But in the UK, overly soft water is much less common than overly hard.
The limescale problem
Hard water doesn't just affect taste - it destroys equipment. Limescale builds up inside boilers, heating elements, pipes, and valves. Over time, it reduces water flow, messes with temperature stability, and eventually causes parts to fail.
We've seen commercial machines ruined in under two years because nobody fitted a water filter. A new boiler or heat exchanger can cost hundreds or even thousands of pounds. A water filter costs a fraction of that. It's one of the best investments you can make for your equipment.
What a water filter does
A commercial water filter sits on your mains supply between the wall and the machine. It typically does three things:
- Reduces limescale by removing excess calcium and magnesium
- Removes chlorine which affects taste (that swimming pool note some tap water has)
- Filters sediment which can block valves and solenoids over time
Good filters reduce hardness without stripping out all the minerals - you want some left for flavour. Most commercial filters are designed to find that balance.
Which filter do you need?
It depends on your water hardness and your volume. Most espresso machine manufacturers recommend specific filters for their machines, and your water company can tell you the hardness level in your area.
As a rough guide: if you're in a hard water area and running a busy cafe, you'll want a filter that handles at least 2,000–4,000 litres before needing a cartridge change. For an office or lower-volume setup, smaller filters are fine.
Cartridges need replacing on schedule - usually every 6–12 months, or when the capacity is reached (whichever comes first). Mark the installation date on the filter so you don't lose track.
Signs your water might be the problem
If you're experiencing any of these and you can't explain it with the coffee or the grind, water could be the culprit:
- Coffee tastes flat, dull, or chalky despite using fresh beans
- White residue building up around the steam wand or in the drip tray
- The machine is running hotter or colder than usual
- Water flow through the group head seems to be slowing down
- A bitter or chemical taste that doesn't go away with different coffee
At home
If you're making coffee at home, the same principles apply on a smaller scale. A simple jug filter (like a Brita) can make a noticeable difference to the taste of your coffee, especially if you're in a hard water area. It won't protect your machine the way a commercial filter does, but it'll improve what ends up in your cup.
For home espresso machines, some models have built-in water filters. Use them, and replace them on schedule.
Not sure about your water? Give David a call. We can advise on the right filtration for your setup and make sure your equipment is protected. It's one of those things that's much cheaper to prevent than to fix.