Plate XIV · section 04 of 13

The standard, and the zones that do not coincide

Close-up of a faucet tip, its grille clogged with limescale deposits — Faucet scaled up by hard water, in southern Arizona: tap water takes its minerals from limestone, and often falls outside the zones recommended for coffeeBbypnda · CC BY-SA 3.0

Parameter	SCA target	Acceptable
Chlorine, odor	none
Total dissolved solids (TDS)	150 mg/L	75-250
Calcium hardness	68 mg/L CaCO₃	17-85
Total alkalinity	40 mg/L CaCO₃	close to 40
pH	7,0	6,5-7,5
Sodium	10 mg/L	close to 10

SCA, Water Quality Handbook; list reproduced by Gagné 2018, p. 2

On a graph of hardness against alkalinity, the tap waters of big cities line up along a diagonal where the two are equal, because water takes its minerals by dissolving limestone; filter pitchers shift the composition along that same line, toward zero. All the recommendations, SCA, Colonna-Dashwood and Hendon, Zurich, and all the published recipes, are relatively soft waters, hardness under 200 ppm and alkalinity between 20 and 80; most cities in the world have much harder water.

Paris, for example: 90 mg/L of calcium, 6 of magnesium, 220 of bicarbonates, 10 of sodium, 420 mg/L of total dissolved solids, that is, a hardness of about 250 ppm CaCO₃ and an alkalinity of about 180, outside every zone. The SCA aims at taste; the SCAE drew a narrower zone, alkalinity 40 to 75 and hardness 50 to 175, dictated by scaling and corrosion of machines; the two overlap only in part.

Water	Ca	Mg	HCO₃	Na	GH	KH
Paris, tap	90	6	220	10	≈ 249	≈ 180
Reverse osmosis	≈ 2	≈ 0,5	≈ 6	≈ 1	≈ 7	≈ 5
Distilled	0	0	0	0	0	0

Eau de Paris, mineral content table (2026), mg/L; GH and KH calculated; osmosis: order of magnitude, Gagné 2021, p. 30

Zone	Alkalinity	Hardness	What it aims at
SCA target	40	68	taste
SCA acceptable	≈ 40	17-85	taste
SCAE core	40-75	50-175	the machines
Published recipes	40	80-94	the filter
Zurich 2015	20 preferred		sensory trial

SCA; SCAE; Gagné 2021, pp. 23-27 and 34

The professional cupping protocol calls for pure, odorless water at between 50 and 150 ppm of total dissolved solids, heated to between 90 and 95 °C, 93 being ideal.

Gagné 2021, pp. 26-27, composition graph; Eau de Paris, water quality, mineral content table (accessed September 7, 2026); SCAE water chart; professional training document, tasting guide, p. 5

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The standard, and the zones that do not coincide