Researchers at Johannes Gutenberg University Mainz have reconstructed Pompeii’s ancient water supply for public baths using carbonate deposits from wells, pipes, water towers, and bath pools. The study focuses on how bathing facilities transitioned from deep wells with water-lifting devices to an aqueduct system in the first century AD, and what that meant for water availability and bath operation.
The team analyzed carbonates formed within different infrastructure components using isotope analysis, comparing stable isotopes and trace elements. Carbonates associated with the aqueduct showed geochemical signatures distinct from those formed in well-related deposits. These differences allowed the researchers to attribute water sources and infer changes in water management, including the use of highly mineralized groundwater drawn from volcanic deposits.
In the Republican Baths, dated to around 130 BC, isotope results indicated that bath water came from wells and was not renewed regularly. The researchers conclude that water was likely replaced only once daily, consistent with supply via a slave-powered treadwheel water-lifting machine. Peaks of lead, zinc, and copper in anthropogenic carbonates point to heavy-metal contamination, which the study links to replacement of boilers and water pipes; oxygen isotope shifts also indicate warmer pool water after renovation.
The carbonate record from wells also showed cyclic patterns in carbon isotope ratios. The study proposes that fluctuating volcanic carbon dioxide in groundwater could be a cause, potentially providing information on Mount Vesuvius activity before the AD 79 eruption. The results were published in Proceedings of the National Academy of Sciences on 12 January 2026 (DOI: 10.1073/pnas.2517276122).
