How to Read a Bottled Water Analysis: TDS, Calcium, pH

A bottled water analysis is a table of what a laboratory found in one sample: the main minerals, the pH, and sometimes total dissolved solids (TDS). Check the units, the date and the uncertainty first, then the minerals, and treat pH and TDS as descriptions of chemistry and taste, not quality scores.

What does a water analysis actually list?

Mostly dissolved salts, which water picks up from the rock and soil it passes through. The positive ones are calcium, magnesium, sodium and potassium. The negative ones are bicarbonate, chloride, sulfate and nitrate. Some reports add silica. Then comes pH, and often a TDS or dry residue figure that sums up the dissolved material.

Units are almost always mg/l, milligrams per litre. Names vary: natrium on a Nordic label is sodium, which is what FRØYA’s bottle and website call it, while the Eurofins report says “Sodium Na”.

What do FRØYA’s numbers say?

The source document is Eurofins report AR-18-MO-004161-02, dated 11 April 2018. The sample, marked “Forsand Water” (no. 440-2018-0322-040), was taken on 20 March 2018. The headline results are:

Calcium: 16 mg/l
Magnesium: 1.1 mg/l
Sodium: 4.8 mg/l
Chloride: 8.5 mg/l
Sulfate: 5.0 mg/l
pH: 7.9, measured at 22.4 °C

The label prints pH as below 7.9, while the report gives 7.9, so the report is the more precise source. You can see the full table on the analysis page and the scanned pages on the certificates page.

Add up the five minerals and you get 35.4 mg/l. Please don’t read that as TDS. The report doesn’t list bicarbonate, potassium, silica or nitrate, so we can’t give a TDS for FRØYA without inventing one. A newer analysis with a dry residue figure would settle it.

What is TDS, and what is a good number?

TDS is total dissolved solids: the inorganic salts, plus a little organic matter, dissolved in the water. The World Health Organization says it is made up mostly of calcium, magnesium, sodium, potassium, carbonate, chloride, sulfate and nitrate. It sets no health-based guideline value for TDS. What it does give is a taste scale from tasting panels: excellent below 300 mg/l, good from 300 to 600, fair from 600 to 900, and worse above that. It also notes that extremely low TDS can taste flat.

Published figures from other premium waters show the spread. Svalbarði lists 21 mg/l. Voss’s Norwegian still water analysis gives 40. Fiji’s February 2025 report gives 220, and Evian lists a dry residue of 345 mg/l at 180 °C. None of these is a better or worse water. They are different tastes.

One caution: TDS is often estimated from electrical conductivity, while Evian reports dry residue by evaporation. The two methods don’t give identical numbers, so treat comparisons as rough.

Does pH matter?

Less than the marketing suggests. WHO describes pH as an operational parameter, mostly about keeping pipes from corroding and disinfection working. It proposes no health-based guideline value, and the usual working range is 6.5 to 8.5.

On published figures, Voss sits at 5.8, Svalbarði at 6, Evian at 7.2, Fiji at 7.89 and FRØYA’s 2018 sample at 7.9. A pH of 5.8 isn’t a defect and 7.9 isn’t a prize. It describes the chemistry of that sample on that day.

How do calcium, magnesium and sodium compare?

Calcium and magnesium together decide how hard or soft a water is, which we cover in our post on soft water and low sodium. For orientation, here are the figures the brands themselves publish.

Calcium runs from 2.7 mg/l in Voss’s Norwegian still water, to 16 in FRØYA, 18 in Fiji and 80 in Evian. Magnesium runs from 0.61 in Voss, to 1.1 in FRØYA, 14 in Fiji and 26 in Evian. Sodium runs from 3 mg/l in Voss, to 4.8 in FRØYA, 6.5 in Evian and 16 in Fiji. Each brand’s figures come from its own published analysis, linked below, and brands update them, so check the current page before quoting anyone.

What are LOQ and MU, and why do they matter?

The footnotes of FRØYA’s report define LOQ as the limit of quantification, the smallest amount the method can measure reliably. MU is measurement uncertainty. Every lab result is a best estimate with a margin around it, and the report states that margin for each line.

Calcium is 16 mg/l with an MU of 15%. Read as a relative uncertainty, that puts the true value somewhere around 13.6 to 18.4 mg/l. Sodium at 4.8 mg/l has an MU of 20%, magnesium at 1.1 has 15%, chloride at 8.5 has 10%, sulfate at 5.0 has 15% and pH at 7.9 has 3%. The practical lesson: a difference of 4.8 against 5.0 mg/l of sodium between two waters is noise, not a ranking.

The report also says results apply only to the examined sample, and that measurement uncertainty has not been considered in judging whether a result is outside a limit. Read it as a snapshot.

What should you check before trusting a label?

The date of the analysis. FRØYA’s is from spring 2018.
The laboratory. This report is issued by Eurofins in Moss, Norway, with the analyses run by Eurofins labs in Lidköping, Sweden, whose ISO/IEC 17025 accreditation it cites.
A sample reference that ties the paper to the product.
The units, and whether the figure is a measurement or a rounded label number.
Whether the numbers on the bottle match the report behind them.

Frequently asked questions

What is a good TDS for drinking water?

WHO sets no health-based guideline for TDS. Tasting panels rated water below 300 mg/l as excellent and 300 to 600 mg/l as good, and extremely low TDS can taste flat. Which end you prefer is a matter of taste.

What does natrium mean on a water label?

Natrium is the Nordic and Latin name for sodium. FRØYA’s label lists natrium 4.8 mg/l, and the Eurofins report lists the same result as sodium.

Is higher pH water better?

No evidence in WHO’s guidance says so. WHO treats pH as an operational parameter, mainly about corrosion and disinfection, and proposes no health-based guideline value.

What is in FRØYA water?

According to the 2018 Eurofins report: calcium 16 mg/l, magnesium 1.1 mg/l, sodium 4.8 mg/l, chloride 8.5 mg/l, sulfate 5.0 mg/l and pH 7.9. Sugars, protein and fat are below the limits of quantification.

How old is FRØYA’s water analysis?

The sample was taken on 20 March 2018 and the report is dated 11 April 2018. It covers one sample and applies only to that sample.

Sources

Figures for FRØYA come from Eurofins report AR-18-MO-004161-02 (sample taken 20 March 2018, report dated 11 April 2018), which covers one sample. Figures for other brands are taken from the pages linked above and may have changed since. This article is general information about water, not medical advice.

How to Read a Bottled Water Analysis: TDS, Calcium, pH and More