Clearing a blocked drain and fixing why it blocks are two different jobs, and on Marrickville's older lines they are easy to confuse.
Clearing restores the flow. A machine or jet cuts through the roots and build up and the water runs again. On a pipe that is sound apart from the blockage, that is the whole job.
Where the blockage keeps returning to the same place, clearing alone is only buying time. The reliable next step is a camera inspection, which shows whether the cause is a cracked joint, a root mass, a sag in the line or a section that has partly collapsed. That is what tells you whether the pipe needs a repair, a relined section, or simply a scheduled clean.
It matters because the fix is different for each. A cracked joint letting roots in can often be relined without digging. A pipe that has lost its fall will keep pooling and blocking no matter how often it is cleared, because clearing cannot change the grade. Anyone quoting a permanent fix without putting a camera down the line first is guessing.
If a drain is surcharging and water or sewage is backing up inside, stop using fixtures that drain to that line, keep clear of any wet electrical fittings, and call for help. Do not try to clear a surcharging sewer yourself, because the water can carry contamination.