The present study aimed to analyze the physicochemical properties and biological activity of an L-malic acid descaler. The treated water with L-malic acid descaler complies with EU Directive No. 2020/2184 for the quality of water intended for human consumption. The L-malic acid descaler contains L-malic acid as the active component, while polyethylene and activated charcoal function as structural and absorbent materials, respectively. The composition was analyzed in a licensed laboratory using Chemical Abstracts Service Number (CAS) and European List of Notified Chemical Substances (EINECS) standards. Fourier Transform Infrared (FT-IR) analysis confirmed the presence of hydroxyl (–OH), carbonyl (C=O), and carboxyl (–COOH) groups in L-malic acid descaler, which are connected with proton-donating ability, and redox activity. The biological activity was evaluated using Saccharomyces cerevisiae as a model system. The role of the YAP1 transcription factor, a key regulator of oxidative stress defense mechanisms, was also examined. The detrimental effects on a cellular level were induced by the well-known mutagen—methyl methanesulfonate (MMS). Our data revealed that yeast cells treated with such water decrease the MMS-induced superoxide anions (3.5-fold), total glutathione lipid peroxidation (1.5-fold), and total glutathione (3-fold) and increase cell survival (2-fold). In conclusion, water treated with L-malic acid descaler possesses antioxidant effects in yeast-cell-based tests, independent of YAP1 transcription factor activity. This study provides preliminary evidence that L-malic acid, when dissolved in water, significantly reduced MMS-induced superoxide anions, one of the biomarkers contributing to the genotoxic and carcinogenic effects of MMS.