In granitic regions, waters are weakly mineralized, with high concentrations in carbon dioxide, because of insoluble and hardly hydrolysable soils. These acidic waters are considered as agressive and must be treated by filtration on limestone materials to reach calco-carbonic equilibrium. Marine and terrestrial limestone materials are usually used but the company, Usine de Kervellerin, wants to develop a new remineralization opportunity by using a shell co-product. Semi-industrial scale tests were thus conducted directly on water treatment plants, in Couzeix and Ambazac. The reactivity and efficiency of the shell coproduct were comparable to usual materials for contact times between 15 and 20 minutes.