Water and Espresso Coffee

By Christopher Short

Coffee aficionados love to discuss the elements that make for their perfect cup. Factors often mentioned are their favorite brand of coffee beans, the proportion of arabica to robusta beans, the type of roast and single versus double boiler espresso machines, just to name a few. Interestingly, one issue only occasionally considered is that of water quality. This is odd given that water constitutes 95% of an espresso.

The reason it is not top of the list is probably because few really know what attributes they should be looking for in water and they generally have little choice in the matter. For most of us, it just arrives, normally out of the tap. The reason we should be concerned about water quality is that it does affect the taste of your coffee and it has a significant effect on brewing equipment performance and reliability in many regions.

Water could be referred to as ‘the universal solvent’. It will dissolve almost anything to some degree. As rain falls to earth it takes up airborne gases like car and truck exhaust fumes and industry air pollution. This is why the air smells so fresh after a good rain. Once on the ground the water soaks in, dissolving naturally occurring calcium, magnesium, iron and other elements as well as ground pollution. In addition, water collects particulate matter (commonly called dirt!) that will not dissolve but is carried in suspension.

To improve water quality, public water authorities treat the water to remove most of the dirt particles and to disinfect it. The most common way to disinfect water is through the addition of chlorine, which will inevitably alter the taste of the coffee. Installation of appropriate water filters will remove the chlorine from the water and will ensure that any dirt particles are removed. Some people prefer to use rainwater in their home espresso machines. It is imperative to use a water filter before filling the water tank to remove the dirt particles and, if the correct filter is used, the dissolved air pollution.

Another issue involving water is that of water ‘hardness’ – that is, the content of calcium and magnesium in the water. Higher levels constitute harder water. The reason water gets hard is by the percolation of ground water through calcium and magnesium-laden soils. Water hardness is not removed by filtration and has no health effects. In fact, many bottled mineral waters are exceptionally hard. It is interesting that espresso made from hard water tastes better. The reason is that flavour extraction from ground beans increases with harder water. However, there is a limit – beyond 90 parts per million (ppm) of calcium carbonate, flavour extraction does not increase. This would be fine except that hard water (150ppm and above) causes significant build up of calcium scale in coffee brewing equipment. A way of avoiding this is to use a water softener, which replaces the calcium content with sodium. This is why water softeners must occasionally be regenerated with sodium chloride (common salt), which is the source of the sodium.

Softening water will reduce the problem of hard water scale build up in the machine but it will, to a degree, alter the taste of the coffee. Alternatively, the use of unsoftened (but still filtered) water will enhance the taste but necessitate occasional descaling of the machine. Non-carbonated spring or mineral water can be used effectively in home espresso machines with water tanks. These waters are generally of moderate hardness and are filtered, providing good quality water for espresso.

In summary, for better tasting coffee, moderately hard water is fine but ensure it is filtered and that you descale your machine occasionally.

Christopher Short is Managing Director of Adelaide-based cleaning products company, Cafetto.

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One Response to “Water and Espresso Coffee”

  1. cafedave.net » Water and Espresso Coffee Says:

    [...] Magazine] Water and Espresso Coffee – how water hardness in particular contributes to the taste of coffee, and what impact that will [...]


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