Are mineralisation and dry residue the same thing?

Almost. Dry residue is the mass of salts left after evaporation at 180 °C. Mineralisation is the sum of the ions from the analysis, and it usually comes out slightly higher, because some of the bicarbonate breaks down during evaporation.

What pH is best for drinking water?

The standards allow a pH from 6-6.5 up to 9-9.5. Within that range, pH affects the taste rather than the quality of the water.

How do I convert hardness from mg/L of calcium carbonate to meq/L?

Divide by 50. The Thai limit of 100 mg/L works out as 2 meq/L, three and a half times stricter than the Russian limit for tap water.

Why does the label say "Na + K" instead of sodium on its own?

That is the convention in Russian mineral water standards. These waters usually contain far less potassium than sodium, so you can read the figure as almost entirely sodium.

What does "suitable for a low-sodium diet" mean?

Under EU rules such water contains less than 20 mg of sodium per litre. If you have been told to cut down on salt, look for this line and discuss your choice of water with your doctor.

Composition and health · 9 min · 17 September 2026

Water passport: a glossary of mineralisation, pH, hardness and ions

What TDS, pH, hardness, CO₂, calcium, magnesium, sodium and other label lines mean, with EU thresholds in mg/L.

In short: mineralisation shows how much salt there is in a litre (table water goes up to 1 g/L). pH tells you about acidity, hardness about calcium and magnesium. An individual ion becomes worth naming once it passes a threshold: under EU rules that means more than 600 mg/L of bicarbonate, more than 150 of calcium, more than 50 of magnesium and more than 200 of sodium. Below 20 mg/L of sodium, the water is suitable for a low-salt diet.

Mineralisation and TDS

Total mineralisation is the sum of all dissolved ions in a litre, printed in mg/L or g/L; in English it is TDS, total dissolved solids. A household TDS meter works it out from electrical conductivity, so its reading is only approximate. Under GOST R 54316-2020, water up to 1 g/L is fresh, 1-2 g/L slightly mineralised, 2-5 low-mineralised and 5-10 medium-mineralised. Under EU rules, up to 50 mg/L is a very low mineral content, up to 500 mg/L is low, and above 1500 mg/L the water is rich in mineral salts.

Total mineralisation is the sum of all dissolved ions and molecules in a litre, printed in mg/L or g/L
TDS (total dissolved solids) is the same figure under its English name. A household TDS meter derives it from conductivity, so the reading is approximate
Under GOST R 54316-2020, water up to 1 g/L is fresh, 1-2 g/L slightly mineralised, 2-5 g/L low-mineralised, 5-10 g/L medium-mineralised and 10-15 g/L highly mineralised
Under EU Directive 2009/54, water up to 50 mg/L has a very low mineral content, up to 500 mg/L a low one, and above 1500 mg/L it is rich in mineral salts
For comparison: Icelandic Glacial has 62 mg/L, Narzan 2-3.5 g/L and Essentuki No. 4 7-10 g/L

pH, hardness and CO₂

These are the three lines most often misread. pH shows acidity: 7 is neutral, higher is alkaline. The Russian SanPiN allows 6-9 and the EU 6.5-9.5, and within those bounds pH affects taste rather than quality. Hardness is calcium plus magnesium: Russia counts it in meq/L with a limit of 7 for tap water, Thailand in mg/L of calcium carbonate with a limit of 100 for bottled water. CO₂ is dissolved carbon dioxide; in Narzan it comes from the spring itself, at around 2.5 g/L.

pH shows acidity. At 7 water is neutral, below 7 acidic, above 7 alkaline. The SanPiN allows 6-9 for drinking water, the EU 6.5-9.5
Icelandic Glacial has a pH of 8.4 according to the brand, and 6ty Degrees 8.5. Water like this tastes soft, but pH does not tell you whether a water is good for you
Hardness is calcium plus magnesium. Russia counts it in meq/L, with a limit of 7 for tap water. Thailand counts it in mg/L of calcium carbonate, with a limit of 100 for bottled water
CO₂ is dissolved carbon dioxide. In Narzan it is natural, around 2.5 g/L in the 2023 batch analyses. In the EU, water with more than 250 mg/L of free CO₂ may be called acidic

How much calcium, magnesium and sodium is in mineral water?

Under EU rules, water is called calcic from 150 mg/L of calcium, magnesic from 50 mg/L of magnesium and sodic from 200 mg/L of sodium. Narzan clears the first two thresholds: 200-600 mg/L of calcium and 50-180 mg/L of magnesium on the label, and 361-381 mg/L of calcium in the 2023 batch analyses. Essentuki No. 4 carries 2000-3000 mg/L of sodium with potassium, which is the key figure for anyone counting salt, since the WHO advises adults to stay under 2 g of sodium a day. Lithium appears only in trace amounts.

Calcium (Ca): under EU rules a calcic water starts at 150 mg/L. Narzan lists 200-600 mg/L on the label and 361-381 mg/L in the 2023 batch analyses
Magnesium (Mg): the EU threshold is 50 mg/L. Narzan has 50-180 mg/L. A lot of magnesium gives a slightly bitter note, which is why the SanPiN caps it at 50 mg/L in tap water
Sodium (Na) and potassium (K) are often printed as a single line on Russian labels. In the EU, a sodic water starts at 200 mg/L of sodium. The wording "suitable for a low-sodium diet" is allowed below 20 mg/L of sodium
Essentuki No. 4 has 2000-3000 mg/L of sodium with potassium. The WHO advises adults to stay under 2 g of sodium a day, so a 0.45 L bottle accounts for a noticeable share of that
Lithium (Li) occurs in mineral water in trace amounts. In Russian tap water the limit is 0.03 mg/L

Anions: HCO₃, SO₄, Cl, F, NO₃

Anions are what you taste. Bicarbonates soften the taste: in the EU a bicarbonate water starts at 600 mg/L of HCO₃, and Narzan has 1000-1950 mg/L while Essentuki No. 4 has 3400-4850. Sulphates add a light bitterness, with a threshold of 200 mg/L; Narzan has 250-1100. Chlorides bring a salty note, also from 200 mg/L; Essentuki No. 4 has 1300-2000. Fluoride and nitrate stand apart in this list: they are safety figures, not taste figures.

Bicarbonates (HCO₃) soften the taste. The EU threshold for a bicarbonate water is above 600 mg/L. Narzan has 1000-1950 and Essentuki No. 4 3400-4850 mg/L
Sulphates (SO₄) add a light bitterness. The EU threshold is above 200 mg/L; Narzan has 250-1100 mg/L
Chlorides (Cl) bring a salty note. The EU threshold is above 200 mg/L; Essentuki No. 4 has 1300-2000 mg/L
Fluorides (F): in the EU a fluoridated water starts at 1 mg/L. Above 1.5 mg/L the water is not recommended for children under 7 on a regular basis
Nitrates (NO₃) are a pollution marker, not a mineral you want. The WHO and EU limit is 50 mg/L, the SanPiN limit 45 mg/L

Silica and boron

These two lines on the label alarm people for no reason. Silica is printed as metasilicic acid, H₂SiO₃: Essentuki No. 4 has 10-60 mg/L of it and Narzan 10-50 mg/L. Boron appears as orthoboric acid, H₃BO₃, and Essentuki No. 4 has 30-70 mg/L, which is why the word "boric" is part of its description. Both are natural and come from the spring itself. For tap water the SanPiN caps boron at 0.5 mg/L, but that limit does not apply to medicinal-table waters.

Silica is printed on labels as metasilicic acid, H₂SiO₃. Essentuki No. 4 has 10-60 mg/L of it and Narzan 10-50 mg/L
Boron is printed as orthoboric acid, H₃BO₃. Essentuki No. 4 has 30-70 mg/L, which is why the word "boric" appears in its description
Silica and boron in mineral water are natural components of the spring. For tap water the SanPiN caps boron at 0.5 mg/L, but that limit does not apply to medicinal-table waters
All the figures come from labels and from GOST R 54316-2020. The composition of a natural water shifts slightly over time, which is why a range is printed