Access to safe and affordable drinking water remains a challenge with 2 billion people still lacking access worldwide. Passive in-line chlorination holds promise for resource-limited rural settings. The A’J´ın chlorinator is a low-cost, handmade passive in-line chlorination device promoted by Helvetas Guatemala. This study evaluated the acceptance of the A’J´ın chlorinator and its effectiveness in reducing bacterial contamination in tap and drinking water in 14 water distribution system (9 control, 5 treatment) rural Guatemala. We held household and operator surveys, and monitored E. coli and total coliform presence, pH, temperature, turbidity and free residual chlorine (FRC) concentration at reservoir tanks and of tap water and household drinking water. 1 The findings demonstrated that passive chlorination significantly reduced E. coli presence in tap and drinking water. Initially, 28% of taps and 25% of drinking water samples tested positive for E. coli, which decreased to 1% and 15% respectively in the WDS actively using the A’J´ın device. A rather low chlorine dosing consistency was observed, with only 24% of collected tap samples meeting the recommended minimal free residual chlorine (FRC) threshold of 0.2mg/L. Despite detectable FRC, some tap and household drinking water samples still exhibited bacterial contamination. The device’s low cost and accessibility were overshadowed by operational challenges, high maintenance needs and frequent clogging. To ensure the future success of passive chlorination, we recommend prioritising ease of use combined with low maintenance needs.