Coffee machine water filter: is it needed?

Reading time: ~9 minutes

What does a water filter in a coffee machine do?

A water filter for a coffee machine does two things. It lowers the hardness of the water, so less limescale is left behind on the heating element and in the pipes. And it uses activated carbon to remove chlorine and odours, making the coffee taste cleaner. That's useful, but it's a maintenance product for your appliance, not water purification for your household.

At PureFilter, we see that customers who start out with this topic almost always make the same mental leap: if my coffee machine needs a filter, what's in the water I simply drink without a machine? That's a fair question, and the answer has nothing to do with your coffee. If you want the overview first, read which water filter suits your situation before you reorder a cartridge.

Appliance filter or mains filter: the difference people often get wrong

This is the point where most search results confuse you. "Water filter" means something different in the coffee world than in the water world. Both are called that, they sit in a different place and they solve a different problem.

• Appliance filter: sits in the reservoir of your machine, protects that one appliance against limescale, doesn't remove PFAS or medicine residues, capacity dozens to a few hundred litres.
• Mains filter: sits under your sink on the cold water pipe, filters all the water that comes out of your tap, removes more than 100 contaminants, capacity 15,000 to 20,000 litres.

So an appliance filter doesn't make your water purer, it makes it softer. You see that difference reflected in the certification. An under-sink system like the PureFilter Mineral+ is tested to NSF standards 42, 53, 61 and 372, with standard 53 specifically covering substances with a health effect. No such health claim exists for coffee cartridges, and manufacturers don't claim one either.

Limescale: why your water hardness plays the lead role

Whether a coffee filter is worthwhile depends almost entirely on one figure: the hardness of your tap water. Dutch drinking water companies express this in German degrees of hardness. Waterbedrijf Groningen uses the standard scale: 0 to 4 °dH is very soft, 4 to 8 soft, 8 to 12 average, 12 to 18 fairly hard and 18 to 30 very hard.

Your value is on the website of your own water company. Vitens publishes hardness by postcode, and other suppliers do the same. We've also set the figures per region side by side in our overview of water hardness by municipality, so you can see at a glance whether you live in a limescale area.

Note one thing that coffee specialists rightly emphasise: you don't want ALL the limescale gone. Calcium and magnesium contribute to extraction, and fully demineralised water gives flat coffee and can corrode components over the long term. That's exactly why we don't treat filtering limescale from tap water as "strip everything out", and why the Mineral+ actually returns calcium, magnesium and potassium to the water via Swedish Mineral Rock™.

Per brand: Philips, De'Longhi, Siemens, Jura and Sage

Each brand has its own cartridge with its own shape, and they aren't interchangeable. These are the types you come across most often in the Netherlands, with the prices that appeared in Dutch Google results at the time of writing.

Philips and Saeco: AquaClean

The best-known cartridge in the Netherlands, with the code CA6903. Philips links AquaClean to a counter in the menu: you activate the filter and the machine tracks how many litres have passed through. The idea is that you only need to descale after wearing out a series of filters. That only works if you actually replace and activate the filter on time. Forget it, and the counter keeps running while the machine scales up anyway. More about this brand is in our Philips water filter review.

De'Longhi: DLSC002

The cartridge for the ECAM series, often the cheapest of the five. With De'Longhi you set the water hardness separately in the menu, and that setting determines how quickly the machine asks for descaling. Set it to soft while your water is fairly hard, and the machine thinks it's not so bad.

Siemens and Bosch: Brita Intenza

Siemens and Bosch work with a Brita cartridge, with Siemens under the code TZ70003. That's the same brand you know from filter jugs, in a different housing. The principle is identical to that jug: ion exchange plus activated carbon. We describe how that technology compares to a fixed system in our Brita water filter review.

Jura: Claris

Jura uses the Claris line, including Claris Smart+ with a chip that shows the machine which filter is fitted. The most expensive category in this list, and the reason Jura owners often start doing the maths: with intensive use, this adds up considerably per year.

Sage: ClaroSwiss

For the Barista Express, Pro and Touch. Sage machines are espresso machines with a water tank the cartridge hangs in. With espresso under pressure, stable water is extra noticeable in the shot, so here a filter has a relatively big effect on the taste.

How often should you replace the water filter?

The rule of thumb for appliance filters is every two to three months, or sooner if your machine asks for it. Modern fully automatic machines track this themselves and give a notification; if your machine doesn't have that notification, a fixed date in your diary is safest. Always consult the manual for your model, because capacity varies greatly per cartridge.

Important: a saturated cartridge isn't neutral. It no longer binds limescale and it does sit in standing water, which can actually worsen the water quality in the reservoir. So a filter that's been in too long is worse than no filter. We see that same misconception with fixed systems, which is why we've separately explained how often you should replace a water filter and why you never clean a sealed inline filter but replace it.

Work it out. Four cartridges a year averaging €13 is just over €50, for that one machine alone, and your tea, pasta and drinking water still go unfiltered. A replacement filter for the Mineral+ costs €65.00 per year and treats everything that comes out of the tap.

Is a water filter for a coffee machine nonsense?

No, but it is often overrated. An honest breakdown, in three points.

• It's true that it reduces limescale: in areas with fairly hard water, a cartridge noticeably extends the interval between descaling and protects the boiler.
• It's not true that your machine then stays clean: descaling remains necessary, and the milk system and brew group need their own maintenance regardless.
• It's certainly not true that your water becomes healthier: a coffee cartridge isn't designed to remove PFAS, medicine residues or heavy metals, nor does it claim to.

That last point is what matters to us. Dutch tap water meets the standards, and that remains the case. Still, since October 2022 an indicative guideline value has applied for PFAS in drinking water of 4.4 nanograms per litre, expressed in PFOA equivalents. The RIVM advises that people should not get more than 20 percent of the health-based limit value through drinking water, because the remaining 80 percent comes through food. In more than half of the measurements in drinking water made from river water, that share is now higher. You won't get a substance like that out of your water with a coffee cartridge.

Appliance filter alongside an under-sink filter

The two don't rule each other out, but in practice a fixed filter often makes the cartridge redundant. Water that's already pre-treated coming out of the tap puts much less strain on the cartridge in your machine.

If you have a boiling water tap, the combination is extra relevant: the filter sits ahead of the system on the cold water supply. We explain how that works on our page about the water filter for a Quooker. And if you mainly make tea or like to drink warm water from the tap, drinking warm tap water is a good companion piece to this article.

Buying advice: what do you choose when?

• Soft water and light use: skip the cartridge and descale according to the manual. That's enough.
• Fairly hard water and daily coffee: buy the original cartridge for your brand and replace it every two to three months.
• You also want cleaner drinking water: tackle it at the mains. Then your coffee machine benefits too, and you drink filtered water from the same tap.
• You buy cartridges for multiple appliances: work out your annual costs. A fixed system is often cheaper than the sum of your cartridges.

Still unsure between the options? The best water filter lays them out, or check our range of water filters directly. We sell one system, and that's a deliberate choice: the PureFilter Mineral+ with its matching replacement filters.

Frequently asked questions

Conclusion

A water filter for your coffee machine is a maintenance product: it keeps limescale out of your boiler and chlorine out of your cup, for approximately €9 to €21 per cartridge and a replacement every two to three months. Whether it's worthwhile depends on your water hardness. Below 8 °dH the benefit is small, above 12 °dH it's wise.

What a cartridge like that doesn't do is purify your drinking water. PFAS, medicine residues and heavy metals fall outside its reach, and no health standard is attached to that either. If you're already doing the maths on four cartridges a year, take a look at what happens when you tackle it at the mains instead: one filter that removes more than 100 contaminants, adds minerals back and lasts 15,000 to 20,000 litres, for less than one cent per litre. Your coffee machine benefits too, and so does the rest of your kitchen.