Investigation of the effectiveness of point-of-use (POU) water dispensers in reducing lead and nickel levels in drinking water

• POU water dispensers were investigated as potential sources of metal contamination. • Effectiveness of POU dispensers in reducing drinking water Ni and Pb was explored. • Stainless steel components and solders were main sources of Ni and Pb respectively. • Removal efficiency was enhanced at higher metal concentrations. • The dispensers effectively reduced Pb but showed limited efficiency in Ni removal. While trusted by consumers for safe drinking water, the effectiveness of point-of-use (POU) dispensers in reducing health-relevant heavy metals, such as lead (Pb) and nickel (Ni), and the potential of metal leaching from their internal components remain largely unexplored. This study conducts a detailed investigation of individual component within POU dispensers and their contribution to either the removal or release of Pb and Ni under controlled experimental conditions. Experiments were conducted using synthesized tap water as source water across three scenarios: clean water (no Pb or Ni), low spike (Pb: 10 μg/L, Ni: 20 μg/L), and high spike (Pb and Ni: 100 μg/L). Water samples collected from five downstream points, including post-filtration, storage, transfer, and outlet units, revealed detectable levels of Pb and Ni even under clean water conditions, indicating that component units could be potential sources. Pb levels were effectively reduced to below the local regulatory standard of 10 μg/L across most scenarios, except in hot water systems. Conversely, Ni concentrations frequently surpassed the local regulatory standard of 20 μg/L, particularly in hot water storage and outlet. Stainless steel components and solders were determined to be the sources of Ni and Pb respectively. Our findings recommend the need for a third-party monitoring of the POU dispensers and offer valuable insights to inform evidence-based improvements in material selection and testing, thereby ensuring the safety of drinking water.