Millions of households rely on onsite wastewater treatment systems (OWTSs) to safely treat domestic wastewater; however, OWTSs can become environmental hazards when they are not sited properly or maintained. To better understand the drivers of OWTS maintenance and failure, we examined relationships between site-level OWTS characteristics and system repair, pumping, and anomalous pumping records in Athens-Clarke County, Georgia, USA. We found that the oldest OWTSs (> 50 years) had the highest probabilities of being repaired and exhibiting signs of hydraulic failure. Notably, newer OWTSs (2-10 years) were approximately equally as likely as older systems to exhibit signs of hydraulic failure. These findings suggest that repair and replacement efforts should emphasize older systems that are at or near the end of their serviceable life, and the hydraulic performance of both newer and older OWTSs should be monitored. These insights can aid decision makers in equitably prioritizing wastewater infrastructure investments and policies.