# Romania's mineral springs: Why water tastes of iron or eggs

Three famous springs, three tastes: Borsec sparkles, Covasna brings gas and iron, Herculane smells of rotten eggs. Taste shows the rock the water crossed.

Full edition, with the interactive blend: https://mariuscomper.uk/izvoare-minerale-romania/en/

## The three waters, in brief

- **Borsec**: intensely carbonated, bicarbonate, magnesian. Taste: sparkling, full-bodied, mineral.
- **Covasna**: carbonated with mofette, alkaline-earth with calcium and magnesium. Taste: sparkling, metallic-tasting.
- **Băile Herculane**: sulphurous, thermomineral. Taste: rotten-egg smelling, bitter-astringent, warm.

## Borsec: the water that bites

An analysis published in 2013 records 2,868.4 mg of free carbon dioxide per litre, 1,903.2 mg of bicarbonate, 384.4 mg of calcium and 107.1 mg of magnesium, at a total mineralisation of 2,554 mg per litre. The sampling year is not stated, and figures vary by year and borehole. The gas comes from the mofettic aureole of the Călimani-Harghita volcanic chain. Head springs: Boldizsár (no. 3), László (no. 5), Lázár (no. 6), Kossuth (no. 10), Petőfi (no. 11) and Pierre Curie. Bottling since 1806.

## Covasna: the gas you sit in

Carbon dioxide leaves the ground as gas, in mofettes; carbonated baths and gas emanations serve a cardiology hospital and a children's sanatorium. The water is carbonated, alkaline-earth with calcium and magnesium; the bottled water holds 7.3 mg of manganese per litre.

## Băile Herculane: warm water with sulphur

The thermomineral springs were known and used by the Romans, rediscovered in 1728. The northern springs rise from the limestones of the Hercule hydrostructure, along the tectonic corridor of the Cerna valley. Hercules I varies between 17 and 52 degrees Celsius, flowing between 36 and 132 litres per second. Sulphurous waters (at least one mg of hydrogen sulphide or related sulphur compounds per litre), medicinal waters and thermal baths.

## Three thresholds

1,000 mg of CO2 per litre (carbonated); 10 mg of iron per litre (ferruginous; the metallic taste from 0.3 mg per litre); 1 mg of hydrogen sulphide or related compounds per litre (sulphurous).

## Method and limits

Figures for Borsec come from an analysis published in 2013, with no sampling year. For Covasna and Herculane the page shows classifications and literature values, not laboratory bulletins. Analyses differ by sampling year and borehole. The page gives no treatment guidance.

## Sources

- Constantin Munteanu, Therapeutic mineral waters, Editura Balneară, 2013: http://bioclima.ro/APETERAP.pdf
- Borsec resort presentation, town hall: https://statiuneaborsec.ro/ro/Prezentare-26
- I. Povară, the Băile Herculane thermomineral springs, 1973: https://www.travaux-racovitza.com/journals/downloads/73/art23.pdf
- Neptun Baths dossier, HerculaneProject: https://herculaneproject.ro/en/wp-content/uploads/sites/2/2022/07/Neptun-Baths-Urgent-Safety-Interventions-2.pdf
- US EPA secondary drinking-water standards: https://www.epa.gov/sdwa/secondary-drinking-water-standards-guidance-nuisance-chemicals
- ATSDR hydrogen sulphide fact sheet: https://www.atsdr.cdc.gov/toxfaqs/tfacts114.pdf

Text and page: Marius Comper, September 2026.