The same coffee brewed with two different waters can taste different. If you want to check this for yourself, start with the composition printed on the label. Pay the most attention to bicarbonates, and treat the SCA values as a reference point, not a guarantee of ideal flavour.
Water for filter coffee: how it affects flavour
Bicarbonates help neutralise acids. When there are more of them, the acidity and fruitiness of a coffee can come through less clearly. In a 2026 sensory study, a higher bicarbonate content in the tested coffee was linked to less perceived acidity, fruitiness and complexity, and to more pronounced roasty and bitter notes. This is a result for specific coffees and specific test conditions, not a rule that has to hold for every pour over.
Bicarbonates, water hardness and pH are not the same thing
On the label, look for bicarbonates (HCO₃⁻), calcium and magnesium. Hardness on its own does not let you predict a specific flavour: in the 2026 study, changing it produced no clear sensory differences in the tested coffee. Popular claims that magnesium will always bring out sweetness or floral notes are therefore too categorical.
Don’t treat pH and alkalinity as the same thing either. pH describes how acidic or alkaline the water is, while alkalinity is its capacity to neutralise acids. That is why pH alone is not enough to judge how water will affect the perceived acidity of a coffee.
SCA water standards for coffee: what values do they give?
The values from the SCAE Water Chart and the older SCAA standard are sometimes presented as a single table, even though they refer to different measures of hardness. The SCA states that work on a common water standard for different brewing methods is still in progress. Treat the figures below as industry guidelines, not a recipe that guarantees the best brew.
| Source document | Parameter | Stated value |
|---|---|---|
| SCAE Water Chart, 2015 | Total hardness | 50-175 mg/l as CaCO₃ |
| SCAE Water Chart, 2015 | Alkalinity | 40-75 mg/l as CaCO₃ |
| SCAE Water Chart, 2015 | pH | 6.5-8 |
| Older SCAA standard, 2009 | TDS | target: 150 mg/l; range: 75-250 mg/l |
| Older SCAA standard, 2009 | Calcium hardness | target: 68 mg/l; range: 17-85 mg/l |
| Older SCAA standard, 2009 | Total alkalinity | target: 40 mg/l, “at or near 40” |
| Older SCAA standard, 2009 | pH | target: 7; range: 6.5-7.5 |
| Older SCAA standard, 2009 | Sodium and chlorine | sodium: target 10 mg/l; total chlorine: 0 mg/l |
The SCAE Water Chart gives total hardness, while the older SCAA standard gives calcium hardness. Don’t compare these values as if they described the same parameter.
Water filters for coffee: not all filters do the same job
A filter does not always remove the same components. That is why the label “filtered water” is not enough to predict how the flavour of the coffee will change.
| Treatment method | What does it change in the water? | What is worth knowing when brewing coffee? |
|---|---|---|
| Ion exchange softener | Swaps calcium and magnesium ions for sodium or potassium. It lowers hardness but does not lower alkalinity. | Less scale does not have to mean fewer bicarbonates. |
| Dealkaliser | Lowers hardness and alkalinity. | It can shift the balance between the components that affect perceived acidity. |
| Reverse osmosis | Removes most of the dissolved components. | The composition of the water after reverse osmosis depends on the unit. The water may then be blended with source water to raise its mineral content. |
This is an important distinction: a softener does not work the same way as a dealkaliser, and reverse osmosis does more than just reduce hardness. If you use a filter, check the cartridge description or measure the water after filtration. It is worth comparing the parameters before and after treatment, then brewing the same coffee with the same recipe.
Best water for pour over: how to compare two waters at home
Brew the same coffee with two waters. Don’t change the grind, ratio, temperature or pouring technique. Write down the bicarbonate, calcium and magnesium content from the labels. Then compare the cups: pay attention to acidity, fruitiness, bitterness and aftertaste.
If the waters differ in many parameters, you will notice a difference in the cup, but you won’t be able to tell which component caused it. TDS is not enough for this kind of assessment either: it shows the total amount of dissolved solids, but not what they are.
So what is the best water for filter coffee? There is no single best water for every bean. Start by comparing the bicarbonate content and see which water suits a particular coffee better.
Sources
-
Rune et al., Impact of Water Composition on Coffee Sensory Properties: A Comprehensive Analysis, Journal of Food Science, 2026.
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SCAE, The SCAE Water Chart, 2015.
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SCAA, Water for Brewing Specialty Coffee, version of 21 November 2009.
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Specialty Coffee Association, Water and Coffee Acidity: How to Adapt Your Water for Different Extraction Methods.
Water for filter coffee: frequently asked questions
What is the best water for filter coffee?
There is no single water that is best for every coffee. Choose water with no off smell or taste, check its composition, then compare cups brewed with the same recipe.
How do bicarbonates affect the flavour of coffee?
A higher bicarbonate content can dampen perceived acidity and fruitiness. In a 2026 sensory study, more bicarbonates in the tested coffee were also linked to more pronounced roasty and bitter notes. The effect may depend on the coffee and the brewing conditions.
What water values do SCA documents give?
The 2015 SCAE Water Chart gives 50-175 mg/l as CaCO₃ for total hardness, 40-75 mg/l as CaCO₃ for alkalinity and a pH of 6.5-8. The older 2009 SCAA standard gives, among other things, a TDS range of 75-250 mg/l and calcium hardness of 17-85 mg/l. These are different documents and different measures of hardness, not one shared table.
Do hardness, pH and alkalinity mean the same thing?
No. Hardness is mainly related to calcium and magnesium content. pH describes how acidic or alkaline the water is, while alkalinity is its capacity to neutralise acids.
How do you compare two waters for coffee?
Brew the same coffee with both waters without changing the grind, ratio, temperature or pouring technique. Compare acidity, fruitiness, bitterness and aftertaste. If the waters differ in many parameters, the test will show a difference, but it won’t point to a single component as the cause.
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