A house built before 1950 has a drain system that was designed when cast iron, clay and galvanized steel were the only choices, when cleanouts were an afterthought, and when nobody expected the pipe to still be in service a century later. Much of it is. The lateral is clay or cast iron, the stack is cast iron with lead joints, the branches are galvanized steel, and the whole system has been settling, corroding and growing roots since before anyone alive remembers. A camera inspection of a pre-war house is not a search for whether there is a problem; it is an inventory of which problems, where, and how urgent.
Quick answer: expect a clay or cast iron lateral with failing joints, roots and offsets; a cast iron building drain under the floor with scale and possibly channeling; a cast iron stack with lead joints that have loosened; and galvanized branch lines narrowed by rust to a fraction of their size. Expect no exterior cleanout, so entry is through the stack base, a pulled toilet or the roof vent. Prioritise the lateral and the building drain, because they are the expensive ones, and inspect the branches with a small head where they can be entered at all.
The lateral
Vitrified clay in 2 or 3 ft sections with mortar joints, or cast iron with lead-and-oakum hub joints, running to a street main that may be older still. The clay joints have cracked and let roots in at most of them; the cast iron joints have dried and loosened. Offsets and separations are common from a century of settlement. The connection at the main is usually a hammer tap made in a trench long ago. The camera from whatever entry exists should cover the full length, joint by joint, with the sonde tracing the route because no drawing exists. The clay guide and the lead joint guide cover the two materials.
The building drain
Cast iron under the basement floor or the crawlspace, with lead joints every few feet. Scale is universal; channeling along the invert is common in the kitchen branch and the main run; holes with soil behind them are the finding that explains a damp floor or a smell. A camera from the stack base or an interior cleanout, pushing both toward the lateral and toward the branches, is the inspection that matters most, because this is the pipe under the house. The under-slab cast iron guide applies to crawlspace houses as well.
The stack
Cast iron, vertical, with lead joints at every floor and a hub at every branch. It fails more slowly than the horizontal pipe because it is not wet all the time, but the joints loosen and the base, where it turns horizontal and water hits the invert, corrodes like a building drain. A camera from the roof vent inspects the full height. Inspecting a cast iron stack from the roof covers the entry and findings.
The branches
Galvanized steel, 1.25 to 2 in, threaded, and rusted internally to a bore that may be half its nominal size with a lip at every fitting. They drain slowly, block constantly and eventually leak at a fitting. A 17 mm head on a thin rod inspects what it can enter; where it cannot, the inability is the finding. Replacement with plastic back to the stack is the usual answer. The galvanized guide covers reading them.
Entry without a cleanout
The test tee at the stack base, if there is one. The roof vent for the stack and the drain below it. A pulled toilet for the bathroom branch and the building drain beyond. A floor drain for its own branch. An inspection of a pre-war house usually needs two or three of these, and the first recommendation after it is often to install a two-way cleanout. The cleanout guide covers the options.
Priorities
Lateral and building drain first, because they decide between a liner, a spot repair and a replacement that can cost as much as a car. Stack second. Branches third, because they are cheap to replace and the camera often cannot enter them anyway. The report should say what was inspected, from where, and what could not be reached, because in a house this old the unreachable pipe is a known unknown rather than an assumption of soundness. The historic home buying guide covers the purchase case.
Reading the transition at the foundation
In most pre-war houses the cast iron building drain meets the clay or cast iron lateral at or just outside the foundation wall, and that joint was made in a trench with whatever the plumber had. It is frequently the worst joint on the line: offset by a century of the house settling one way and the yard another, leaking, and rooted. The camera from the stack base reaches it on the way out and from an exterior entry on the way in, and the sonde locate lands at the foundation. It deserves its own entry in the report, because a liner has to pass it and a spot repair there means digging beside the foundation.
What to record
The material of each part of the system and the entry used for each. The condition of the lateral joint by joint, the building drain’s invert, the stack’s joints and base, and which branches were reached. The foundation transition. The absence of a cleanout and the recommendation to add one. Distances for every finding. A pre-war report that says only “old cast iron, some scale” has not inspected the house.
Common questions
Does every pre-1950 house need a new sewer?
No. Many clay and cast iron laterals are lined rather than replaced, and some are sound. The camera decides.
Why can the camera not get into the branches?
Galvanized branches have rusted shut past the point a camera head can enter. That is itself the finding.
Where do I start with no cleanout?
The test tee at the stack base, or the roof vent. Then add a cleanout.
Related guides
See the best sewer cameras for older homes, houses built 1950 to 1975, and buying a home with cast iron drains.