The sections are groups of buried nearly horizontal perforated pipes, built in a manner similar to French drains except that the liquid from the septic tank is supposed to go down the pipes and dissipate into the soil along the way.
Under normal operation, the septic tank remains about 85% full. Then for each new gallon of sewage arriving in the septic tank from the house, a gallon of liquid is supposed to exit the other end of the septic tank on an ongoing basis.
When the ground around the perforated pipes is saturated with rain water, or with fine particulate matter (in sludge) from an improperly maintaind septic tank, or with grease (in scum) from an improperly maintained septic tank then the water will dissipate (purge) so slowly that plumbing in your house backs up. For the second two reasons the pipes have to be dug up and the soil around them carted out and new carted in, or new perforated pipes laid elsewhere as a new section.
Under normal operation, the septic tank remains about 85% full. Then for each new gallon of sewage arriving in the septic tank from the house, a gallon of liquid is supposed to exit the other end of the septic tank on an ongoing basis.
When the ground around the perforated pipes is saturated with rain water, or with fine particulate matter (in sludge) from an improperly maintaind septic tank, or with grease (in scum) from an improperly maintained septic tank then the water will dissipate (purge) so slowly that plumbing in your house backs up. For the second two reasons the pipes have to be dug up and the soil around them carted out and new carted in, or new perforated pipes laid elsewhere as a new section.
