About 25% of U.S. households rely on septic systems, and scientists from 12 land-grant universities are collaborating to better understand the complex physical, chemical and biological processes septic systems rely on. Scientists track the amount of contaminants makingtheir way from septic systems into surface and groundwater, monitor the effects of climate change on septic systems and provide research-based recommendations for septic system designs.Examples of this research include:•University of Rhode Islandstudies show advanced nitrogen-removal septic systems can reduce total nitrogen to levels that meet regulationsfor protecting coastal waters. Modeling from URI scientists shows that more bacteria and phosphorus were released from septic systems in climate change scenarios, and rising water tables are leading to near-shore septic systems with inadequate separation distance between drainfields and groundwater. The scientists estimated thousands of septic systems along the southern coast of Rhode Island would be affected by and need repair due to large flood events.•Minnesotascientists have determined household practices and factors that lead to high septic system performance.•The University of Georgiafound evidence that bacteria from septic systems are reaching streams when water tables are high.Project members developed a website that produces customized manuals for septic systemsto help homeowners take better care of their septic systems. With the help of private companies, Extension educators and policymakers, the team is designing septic systems that function under a wide range of environmental conditions and increasing the number of compliant septic systems.Link to full statement on website: https://landgrantimpacts.tamu.edu/impacts/show/5182