Moving clay can leave a gravity sewer line without the support it needs.
A sewer line relies on steady support and a consistent downhill slope from the house. Around Merkel, clay dries out and contracts, then expands again after rain. That movement can leave one part of a buried line lower than the next, shift a connection, or put stress on a rigid pipe section.
Once a line loses its proper fall, wastewater and paper catch at the low point instead of moving through. A shifted joint can also open enough for surrounding soil to enter the pipe. The immediate problem may look like an ordinary blockage, but repeated clearing does not correct a belly, cracked section, displaced joint, or intrusion at a connection.
Recurring main-line backups that follow wet weather, dry spells, or a low area in the yard deserve a look inside the sewer line. A camera inspection distinguishes buildup from a structural issue in the pipe, so the repair can address both the damaged section and the support beneath it.