The main line, or building drain, is the large pipe that collects every branch inside the house and carries it out through the foundation to the lateral. In basement homes it often runs along a wall or under the floor; in slab homes it is buried in the soil beneath the concrete. Because it sits under finished floors, it gets less attention than the yard line, yet it handles all of the house's waste.
What the camera checks inside the house
- Cast iron condition: scale, tuberculation and channeling, where the bottom of the pipe has worn thin or open
- Joints where branch lines tie in, a common spot for cracks and leaks
- Under-slab sections that have settled with the soil and now hold water
- The house trap, where older homes have one, and the cleanout fittings
- The point where the building drain passes through the foundation and becomes the lateral
Why it matters in slab homes
A leaking drain under a slab can wash soil out from beneath the floor without showing up anywhere until a crack, a damp spot or a smell appears. Camera footage with distance counts, combined with a locate from above, shows where under the floor a problem sits, which helps if anyone later has to cut the concrete.
Pairing it with a lateral scope
Many inspections in Proberta, CA cover both pieces in one visit: the main line inside the house and the lateral outside. Ask when booking whether the access point lets the camera travel both directions, so the report covers the whole path from the house to the public main.
