replacing the filter bed does not always mean to replace the septic tank itself. If the concrete cap on the tank is not cracked or broken, chances are good that there is nothing wrong with the tank itself. But leave the filter bed replacement to the pros. They will handle all of the health inspection requirements (which are mandatory). They will have all of the equipment for digging out the old bed and trucking in all of the new sand and gravel. Definitly not a job for the weekend handyman...