What is the best water for a coffee maker?
For most home coffee makers, start with fresh, drinkable water that suits your local supply and the machine’s manual. Filtered tap water is a sensible option when your water has a noticeable chlorine smell, unpleasant flavour or enough hardness to leave scale, but a filter is not a universal instruction. Some machines specify a filter; others specify a particular water type or hardness range.
The manual for your exact model takes priority. Do not assume that bottled water is always better, or that distilled water is always safer for a coffee machine. Breville’s Barista Express manual, for example, recommends cold filtered water and says not to use de-mineralised or distilled water because it may affect the espresso’s taste and how the machine functions. Another manufacturer or model may give different instructions.
The practical answer is to choose water that is clean and pleasant to brew with, check its mineral content when scale is a problem, and follow the appliance maker’s instructions for filters and descaling.
How water changes coffee and the machine
Water is the main ingredient in brewed coffee. Its minerals and alkalinity affect extraction, while odour and chlorine can affect the cup’s aroma and flavour. The same dissolved minerals also pass through a coffee maker’s heating system. When hard-water minerals deposit on heated parts, they can form scale.
The Specialty Coffee Association’s published Coffee Standards gives a useful coffee-brewing reference point. Its 2018 water table lists:
| Water characteristic | SCA target or acceptable range |
|---|---|
| Odour | Clean, fresh and odour-free |
| Chlorine | None |
| Calcium hardness | 50–175 ppm as CaCO3 |
| Alkalinity | Target of 40 ppm |
| pH | Target of 7.0; acceptable range 6–8 |
These are brewing-water standards, not a universal recipe for every domestic appliance. The SCA describes the target as the most desirable point and the range as meeting the standard. Your local water may not match those figures, and the machine manufacturer may set a different requirement.
Tap, filtered, bottled or distilled water?
Use this comparison as a starting point, then check the machine manual and your local water information.
| Water choice | What it can offer | What to check first |
|---|---|---|
| Tap water | Convenient and usually the simplest option | Hardness, chlorine odour and the manufacturer’s permitted water type |
| Filtered tap water | May reduce some tastes or odours and can change the mineral profile | Whether the filter is designed to reduce hardness, how often it must be replaced and whether the machine requires a specific cartridge |
| Bottled water | Mineral content may be stated on the label, making some products easier to compare | The actual mineral profile, cost, waste and the appliance manual; “bottled” does not automatically mean low-mineral |
| Distilled or de-mineralised water | Very low mineral content | Whether the machine allows it; some manuals warn against it or require minerals for correct operation |
Tap water
Tap water can work well when it tastes acceptable and is within the machine’s instructions. In a hard-water area, you may notice scale on kettles, taps or the coffee maker’s water path. That is a reason to investigate hardness and maintenance, not proof that you must switch to one particular bottled water.
If the water has a strong chlorine smell, a compatible filter may improve the brewing water. Follow the filter maker’s replacement instructions. A filter does not remove every possible contaminant or necessarily soften water, so check what the cartridge is designed to do rather than relying on the word “filtered”.
Filtered water
Filtered water can be a useful middle ground between untreated tap water and buying bottled water. Some coffee machines have a built-in or tank-mounted cartridge. If yours does, fit the specified filter, prepare it as the manual describes and replace it on the stated schedule.
Do not use a generic cartridge just because it fits the tank. Compatibility, filtration method and replacement interval all matter. Keep a note of the date you install a filter, especially if the machine does not display a reminder.
Bottled water
Bottled water varies. Spring or mineral water may contain enough dissolved minerals to affect both extraction and scale, while other products have a lower mineral content. Read the label where one is provided, but still check the machine’s manual.
Bottled water is not automatically a better choice for coffee. It can also make maintenance harder to predict if the mineral profile is unknown or changes between products. If you use it, keep the bottle or label information so you can compare products when the machine’s behaviour changes.
Distilled and de-mineralised water
Distilled water is not a universal solution. Very low-mineral water can be unsuitable for some coffee machines, and it may change how a machine detects water or controls brewing. Breville’s BES870 Barista Express instructions specifically advise against de-mineralised or distilled water for taste and functional reasons.
Other models may give different instructions. Read the manual before using distilled, de-ionised, reverse-osmosis or remineralised water. If the manual is unclear, use the manufacturer’s support page or ask the manufacturer rather than guessing.
What is hard water and what is scale?
Hard water contains more dissolved calcium and magnesium than soft water. When water is heated or evaporates, some of those minerals can remain behind as a solid deposit. That deposit is commonly called limescale or scale.
Scale can collect in a reservoir, boiler, thermoblock, heating element or narrow water path. Possible signs include a slower flow, unusual noise, reduced hot-water delivery, visible flakes or a machine warning. These signs do not prove a particular fault, but they are good reasons to check the manual’s cleaning and descaling instructions.
Scale is different from coffee residue. Coffee oils and grounds need ordinary cleaning; mineral deposits need a descaling process. An espresso machine may need both routine cleaning and periodic descaling.
When should you descale a coffee maker?
Use the schedule in the exact manual first. The right interval depends on the model, water hardness, filter use and how often you brew. A calendar such as “every three months” can be a useful prompt for some machines, but it is not a safe universal rule.
Descale sooner when the manufacturer instructs you to respond to a warning light or message. A change in flow, heating or noise can also justify checking the manual. Do not keep running a machine through a suspected blockage while waiting for a generic schedule.
A safe general descaling sequence is:
- Read the model’s descaling section and identify the approved product and quantity.
- Remove coffee, capsules or grounds, and empty the drip tray if the instructions require it.
- Mix and add the descaling solution exactly as directed. Do not substitute vinegar unless the manufacturer permits it.
- Run the machine’s descaling programme, or follow the manual’s button sequence and timings.
- Rinse the tank and flush the machine with the stated amount of fresh water.
- Check the manual for any filter reset, rinse cycle or recommissioning step.
Never mix cleaning chemicals. Do not open a mains-powered machine to remove scale. If the machine remains blocked or behaves unusually after the documented procedure, contact the manufacturer or a qualified service provider.
For model-specific instructions, see our guides to cleaning an espresso machine, descaling a Nespresso VertuoLine and cleaning and descaling a Keurig. Those pages cover particular machines and should not replace the instructions supplied with a different model.
Filters do not replace descaling
A water filter may reduce some substances that affect taste or scale, but it does not mean a machine never needs descaling. The filter may be overdue for replacement, the water may still contain hardness minerals, or the machine may require a maintenance cycle regardless of the water used.
Breville’s cleaning guidance treats descaling and regular water-filter changes as separate parts of espresso-machine maintenance. Keep both tasks in the machine’s maintenance record. If the manual gives a filter-life counter or a descaling warning, follow that system rather than estimating from taste alone.
Routine coffee cleaning matters too. Coffee oils can build up around a group head, basket or brew path even when the water is soft. For espresso-machine cleaning steps, use the espresso cleaning guide and compare its general advice with your model’s manual.
Model-manual caveats that matter
Water advice changes with the appliance. Before choosing a filter or changing water, check:
- the exact model number and regional manual;
- whether the machine requires a cartridge and which part number fits;
- whether the manual gives a hardness setting or asks you to test the water;
- whether distilled, de-mineralised, reverse-osmosis or softened water is allowed;
- the approved descaler and whether vinegar is prohibited;
- the warning lights, rinse volumes and reset procedure;
- whether the machine’s water advice differs between brewing and cleaning.
This is especially important when moving between brands. A recommendation that suits a Breville espresso machine may not suit a Nespresso, Keurig, Zojirushi or Technivorm machine. For the narrower Nespresso question, see our guide to the best water for a Nespresso machine, then confirm the advice against your model’s current manual. Use the Nespresso machine assistance and user guides for Nespresso-specific instructions, and check the relevant guides for Zojirushi coffee makers or Technivorm Moccamaster models before changing water or descaling products.
A simple water routine for home coffee makers
- Start with fresh water that your machine’s manual permits.
- If the water tastes or smells unpleasant, investigate a compatible filter rather than switching blindly to bottled or distilled water.
- If scale appears, check local hardness and the machine’s maintenance instructions.
- Replace filters on schedule and record the date.
- Descale when the manual, machine warning or water conditions call for it.
- Rinse after descaling and stop using the machine if it develops an unresolved flow, heating or electrical problem.
Water choice is a compatibility decision, not a universal shopping rule. SCA water guidance helps explain the coffee variables, while the manual for your exact coffee maker determines what you should put in its tank and how you should maintain it.
Sources
- Specialty Coffee Association, Coffee Standards and The 2018 SCA Water Quality Handbook. The handbook contains the water-for-brewing standard used for the figures in this article.
- Specialty Coffee Association, Water and the Taste of Coffee. Explains how mineralisation and alkalinity affect coffee flavour.
- Breville, Cleaning & Maintenance. Covers cleaning, descaling and water-filter maintenance.
- Breville, Barista Express BES870 instruction manual. Covers filtered water and the warning against de-mineralised or distilled water for this model.
- Nespresso, Machine assistance and user guides. Use for model-specific Nespresso instructions.
Research checked 24 September 2026. Water formulations, manuals and support pages can change; check the current manual for your model before acting.