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

https://source-wiki.win/index.php/Hydro-Jetting_vs_Traditional_Sewage-disposal_Tank_Cleaning:_When_as_well_as_Why_to_Use_Each

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