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Mirage technical manual
page 11 of 65
Water quality
Since water content in an espresso is more than 90%, the quality of your water supply is highly
important for the taste of your coffee. While too much mineral content will hasten damaging lime scale
build-up inside your Mirage, an absence of minerals will give your espresso a flat taste while also
harming the boilers inside the machine. As a rule of thumb, the amount of total dissolved solids (TDS)
in your water should be 100-150 mg/l (=ppm).
We recommend that you contact your water company for details about your water quality and have a
water expert with knowledge of (local) water quality in espresso-machines help you to determine a
suitable water-treatment system. Below some guiding principles.
Hard water treated with an ion exchange water softener only has calcium replaced, and so it is wise to
further treat your water with an activated carbon or a carbon block water filter. These carbon filters
also remove other impurities that affect taste, but, on their own, are not able to remove water
hardness. Calcium and magnesium in the form of carbonates dissolved in water are the two most
common minerals that make water "hard
”. It is recommended that water hardness is 2-4 German
degrees (35-70 mg/l Ca/Mg carbonate). The water treatment system hooked up to your machine
should establish these values.
The acidity (pH-value) of your water should be close to neutral (pH=7). A lower value (pH
˂ 6.5) will
make your espresso start to taste acidic and is corrosive to the metal parts in your machine. A higher
value (pH
˃ 7.5) results in bland tasting brews although it can also neutralise slightly acidic coffee
grinds. You are advised to check the acidity of your water every once in a while.
Chlorine should not be present in your water since it has a highly corrosive effect on all metal parts
(copper, brass and even stainless steel) inside your machine and makes your espresso smell and
taste awful. Chlorine treated water should therefore not be used in your machine unless chlorine is
removed from the water after the chlorine treatment (e.g. by use of an activated carbon or a carbon
block water filter).
Water Quality Parameter
Target
Acceptable range
Odor
Clean/Fresh, odor free
Color
Clear
Chlorine
0 mg/l
TDS
150 mg/l
75-250 mg/l
Calcium Hardness
51 to 68 mg/l
17 to 85 mg/l
Total Alkalinity
40 mg/l
at or near mg/l
pH
7.0
6.5 to 7.5
Sodium
10 mg/l
at or near 10 mg/l
Table W 2. Water properties for optimum taste. Source: SCAA Technical Standards Committee, 2009.
Any installed water treatment system should take the above into account and also prevent coarse
particles and aggressive components to enter the machine. We do not favour the use of de-scaling
agents in our machines and therefore recommend that the function of the water treatment system is
checked regularly. Not only changes in Alkalinity and Hardness of water, but also temperature have
dramatic effects on scale deposits and/or aggressiveness of water on the machine thus no single
water is optimal for both steam- and coffee boiler. We favour scale deposit over corrosion and advice
the use of the higher hardness value shown in the table below. Flushing the steam boiler will help to
reduce scale deposit in the steam boiler. Drawing lots of hot water reduces the scale-forming induced
by steaming due to removal of pure water.