Household water treatment (HWT) can improve drinking water quality and prevent disease, if used correctly and consistently. While international monitoring suggests that 1.8 billion people practice HWT, these estimates are based on household surveys that may overstate the level of consistent use and do not address microbiological effectiveness. We sought to examine how HWT is practiced among households identified as HWT users according to international monitoring standards. Case studies were conducted in urban and rural Zambia. After a baseline survey (urban: 203 households, rural: 276 households) to identify HWT users, 95 urban and 82 rural households were followed up for 6 weeks. Consistency of HWT reporting was low; only 72.6% of urban and 50.0% of rural households reported to be HWT users in the subsequent visit. Similarly, availability of treated water was low, only 23.3% and 4.2% of urban and rural households, respectively, had treated water on all visits. Drinking water was significantly worse than source water in both settings. Only 19.6% of urban and 2.4% of rural households had drinking water free of thermotolerant coliforms on all visits. Our findings raise questions about the value of the data gathered through the international monitoring of HWT practices as predictors of water quality in the home.