Open lids thoroughly, check inlet and outlet baffles and tees, document fractures or deterioration

https://mag-wiki.win/index.php/Reputable_Sewage-disposal_Tank_Emptying_and_Installation:_Smart,_Cost-Saving_Methods

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