Biosand filters (BSFs) have been used to provide potable water to many communities throughout the world. A significant number of laboratory and field studies have demonstrated the effectiveness of the BSF if utilized properly. However, our prior work suggests that multiple factors contribute to the effectiveness of the BSF in a community setting. These factors include: household education levels (HELs), socio-economic status (SES), additional interventions for sanitation and hygiene, water sources, and the relationship between treatment and storage. A structural equation model (SEM) was constructed to evaluate the contribution of these factors to diarrheal occurrence in impoverished households in two Brazilian communities along the Amazon River. The results of this study showed that HEL was the most important factor in reducing diarrhea, and the presence of a BSF was near ineffective. Furthermore, interventions for sanitation and hygiene as well as SES all contributed to a reduction in diarrheal occurrence. This study demonstrates that SEM can provide a platform to evaluate the complex interaction among factors contributing to a reduction in the occurrence of diarrhea. Furthermore, the results of this study highlight the importance of a holistic approach to the deployment of technology-driven solutions such as the BSF.