How the problem unfolded

Months of slow drains
The kitchen and one bathroom drain slowly; the outdoor lateral seems fine when cleaned.
First camera run
Filmed from the outdoor cleanout toward the street: clean. Filmed back toward the house: heavy scale and a split in the bottom of the cast iron under the floor.
Locating
A locator marks the damaged section under the hallway, a few feet inside the foundation.
Options review
The owner compares lining, a slab cut, tunneling and rerouting.

The two finalists

Lining the building drain

  • Work done from cleanouts with minimal floor removal
  • Requires the pipe to hold its shape around the split
  • Branch connections must be reopened inside the liner

Rerouting new drain line

  • Old under-slab line abandoned
  • New pipe run along a different path
  • More wall or exterior work depending on the route

What the owner asked each contractor

  • Can the split section accept a liner, based on the footage?
  • How many branch lines tie into the damaged run?
  • What floors, cabinets or walls would be opened?
  • Who handles permits? Check with the city if unsure.
  • Is a final camera run included?

Takeaways from the example

Filming in both directions from the cleanout mattered. The lateral to the street was healthy, so a full lateral replacement would have spent money on the wrong pipe.

In a slab home the decision is less about the pipe and more about access. Each method moves the disruption somewhere different: the floor, the walls, the yard or almost nowhere.

Questions for your own house

  1. Has my line been filmed toward the house, not just toward the street?
  2. Where exactly under the floor is any damage?
  3. Which fixtures share that run?

Common questions

Is this based on a real customer?

No. It is a hypothetical example written to explain a common situation in slab-on-grade homes.

Is cast iron always the problem in older slab homes?

Not always, but cast iron drains of that era commonly develop scale and corrosion. Only a camera inspection confirms it.

Could the outside lateral fail later too?

Possibly. Keep the footage as a baseline and re-inspect if symptoms change.

General information for Placentia, not a quote or professional advice. In an emergency, call 911.