Disinfection is a standard water treatment process. Plastics are found in various components of water infrastructure and the presence of microplastics in the water cycle raises environmental and human health concerns. Thus, this research investigated the physicochemical impacts of chlorination and chloramination on seven types of virgin and biofouled polymers (125–250 μm) under three disinfectant doses, three pH conditions in potable and recycled water. Our results indicated that both chlorination and chloramination impacted the seven polymers, with polypropylene (PP), expanded polystyrene (EPS) and polyamide (PA) being most impacted, signalling these as polymers of concern. Surface morphological changes were observed. FTIR spectra revealed cleavage of bonds and formation of carbonyl groups indicating degradation. While disinfection is helpful for treating pathogenic microorganisms, the risks of generating microplastics below detection limits are highlighted. Microplastics in disinfected water can lead to biofilm formation, increased adsorption of contaminants and disinfection by-products, compromising water quality and posing challenges for treatment. This research provides valuable insights into the physicochemical impacts of chlorination and chloramination on polymers, enhancing our understanding of their behaviour and fate in water and wastewater environments. While additional ecotoxicological research is needed to fully understand health implications, our study emphasizes the need for targeted intervention strategies of high-use polymers of concern.