Open covers carefully, check inlet and outlet baffles and tees, file cracks or corrosion

https://source-wiki.win/index.php/Choosing_a_Professional_for_Septic_System_Pumping_and_Cleaning_on_a_Budget

Open lids carefully, check inlet and outlet baffles and tees, file fractures or deterioration, and repair seals to stop groundwater intrusion and exfiltration that can overload the drainfield.