Risers are an extension of the septic tank lid to bring the lid to the surface so access can be made to the tank without digging. In some counties, it has been written into code that risers must be installed on all new tank installations. While risers are not mandatory on all septic tanks, they do eliminate the need to disturb the lawn when excavating to expose the lid for regular maintenance of the tank. All pump chambers should be equipped with a riser so easy access is available if/when service is needed on the pump itself.