Access to safe and affordable drinking water remains a major challenge worldwide, especially in rural areas. While passive in-line chlorination offers a promising approach for providing consistent treatment of water supplies in resource-limited settings, little is known about the factors influencing the uptake and use of these technologies. This study used a controlled pre-post intervention design to evaluate the technical performance and user acceptance of a low-cost and locally constructed chlorinator (the A'J & imath;n) in four water distribution systems in rural Guatemala. Data sources included household surveys (N = 319) and operator interviews (N = 25), with regular monitoring of faecal contamination, pH, temperature and free residual chlorine (FRC) at reservoir tanks, taps and households. Faecal contamination was significantly reduced in water systems actively using the A'J & imath;n device. In these systems, the share of tap and household drinking water samples with detectable E. coli decreased from 28% to 1% and 25% to 15%, respectively. Chlorine dosing consistency with the A'J & imath;n was low, with only 24% of tap samples meeting the recommended minimal FRC threshold of 0.2 mg/L. Overall, the share of users expressing satisfaction with their water increased by 14% in the water distribution systems with the A'J & imath;n and stayed constant for users of control systems. While the device's low cost and simple design offered advantages over other chlorinators on the market, operators reported challenges with high maintenance needs and frequent clogging. To ensure the future success of passive in-line chlorination for small community supplies, we recommend prioritising ease of use combined with external support for addressing maintenance needs.