A push-rod camera goes in through a manhole or rodding eye and records the inside of the pipe: cracks, roots, a collapsed length or a joint that has slipped. Tracing then ties what the camera found to a spot in the garden or footpath, which matters when the run crosses the boundary.
The technician notes pipe material, joint condition and how far along the run each defect sits, then says whether it needs clearing, repair or just watching.
Find the manhole covers and rodding eyes and clear anything parked or planted over them. Ask whether you get a copy of the recording.
City centre terraces often have older clay runs shared between houses, so the camera may have to follow the line past your own wall.