For deep blockages, a standard closet auger won't reach. You will need a heavy-duty motorized sewer snake, which can be rented from hardware stores.
Best for: Sludge or soft blockages.
If the line is slow but not completely stopped, you can use a foaming root killer or an enzyme-based cleaner. Effective for killing invasive tree roots. how to unclog sewage line
Do use standard chemical drain cleaners on a main line—they won’t reach the clog and can damage old pipes. Instead, you’ll need: For deep blockages, a standard closet auger won't reach