Between 2015 and 2019, water samples were collected from seven septic systems in Ontario for analysis of wastewater tracer concentrations. These samples were collected from the septic tanks as well as from groundwater along the septic effluent flow paths. In addition, water samples were collected from a small stream impacted by multiple septic systems in a small rural community. The three wastewater tracers included in this data set are two artificial sweeteners, acesulfame and sucralose, and chloride. Information on the analytical methods used and interpretation of the dataset can be found in the following peer-reviewed publication: Water Research 184: 116124. (2020) https://doi.org/10.1016/j.watres.2020.116124