Even if drinking water of poor rural communities is obtained from a `safe' source, it can become contaminated during storage in the house. To investigate the relative importance of this domestic domain contamination, a 5-week intervention study was conducted. Sixty-seven households in Punjab, Pakistan, were provided with new water storage containers (pitchers): 33 received a traditional wide-necked pitcher normally used in the area and the remaining 34 households received a narrow-necked water storage pitcher, preventing direct hand contact with the water. Results showed that the domestic domain contamination with indicator bacteria is important only when the water source is relatively clean, i.e. contains less than 100 Escherichia coli per 100 ml of water. When the number of E. coli in the water source is above this value, interventions to prevent the domestic contamination would have a minor impact on water quality compared with public domain interventions. Although the bacteriological water quality improved, elimination of direct hand contact with the stored water inside the household could not prevent the occasional occurrence of extreme pollution of the drinking water at its source. This shows that extreme contamination values that are often thought to originate within the domestic domain have to be attributed to the public domain transmission, i.e. filling and washing of the water pitchers. This finding has implications for interventions that aim at the elimination of these extreme contaminations.