The sewer lateral is the private pipe from the house to the city main, or to the septic tank. In most cities you own it to the main, including the part under the street. It fails by cracking, bellying (a sag that holds waste), root intrusion, and, in mid-century houses, by being Orangeburg: a bituminized fiber pipe that ovalizes and collapses. A toilet that flushes on showing day does not test any of that. It tests that today's water found a path.

The sewer-scope guide is how the camera inspection should be done, what a cleanout is, and why a "clear" scope that started in the wrong place is worthless. This page is the defect you are pricing once the video exists, and why the listing was never going to volunteer it.

Cast iron inside the house is a related but different pipe. Scope the building drain and the yard lateral as two runs if both are old.

What it is

Clay tile with joints that roots love, cast iron that channels, Orangeburg from roughly the 1940s to the 1970s, and PVC that is fine unless it was installed with a belly or broken by someone digging. The symptom list is short: recurring backups at the lowest drain, gurgling, a wet spot in the yard along the pipe route, and a history of "we had it snaked." Snaking clears a root mass. It does not fix the joint the roots used.

How to spot it in the listing

Age, large trees between the house and the street, and a finished basement with a bathroom. Remarks almost never say "lateral." They say "new sewer" when someone paid for one, and they say nothing when they snaked it last spring. Prior listings and seller disclosures sometimes mention a backup. Read them. Permits for "sewer repair" are public in a lot of cities. Research beyond the listing includes that permit search. A permit that says "spot repair" is not a new lateral.

Insurance claims for backup, if you can learn about them, are the other tell. You often cannot. The disclosure question "any water backup?" is where you ask anyway.

How to spot it at the showing

Find the cleanout. If there is no cleanout, the scope costs more because someone has to pull a toilet or install one. Run water and watch the lowest shower. Slow drain plus a gurgle in the other fixture is restriction. Do not confuse that with a vent problem, but do not explain it away either. The camera settles it. Order the scope during the inspection, with you or your agent receiving the video, not a one-line "passed."

The real risk

A backup into a finished basement, an emergency dig in January, and a collapsed Orangeburg line that cannot be lined because there is no pipe left round enough to line. Lining (a resin sleeve) is a good repair when the pipe is intact enough to host it. It is a sales pitch when the pipe is a pancake. Replacement by trenchless pipe bursting or by open cut depends on depth, utilities, and whether the run goes under a slab, a deck, or a city street. The street cut and the city bond are the line items that double a cheerful quote.

Insurance and lending

Standard policies exclude drain backups unless you bought the rider, and the rider has a low limit. The failed pipe is wear and tear. You will pay for the lateral. Lenders do not usually ask for a scope. FHA does not either, unless sewage is evident. This is a buyer problem, not an underwriting problem, which is why it gets waived in competitive weeks and regretted in the first hard rain.

Typical cost ranges

Typical ranges, not quotes. Depth and the street dominate.

Camera scope: often $200 to $500, more if a cleanout has to be created.
Spot repair of one broken joint in a shallow yard: commonly $2,000 to $5,000.
Trenchless liner or burst of a straightforward yard lateral: often $5,000 to $15,000.
Open replacement including a street or sidewalk cut: commonly $10,000 to $25,000 or more. Orangeburg full of collapse tends toward replacement, not a liner.
Under-slab building drain is the cast-iron page's number, not this one. Do not let one quote blur them.

Pass, negotiate, or investigate

Investigate with a scope on older houses, treed lots, and any house with a basement bath. The guide linked above is the spec for that scope. Negotiate repair or a credit from the video and a plumber's written method (liner versus replace), not from "roots were noted." Pass when the line is collapsed, the repair requires a street cut the seller will not touch, and you cannot carry the typical range above. A clean video is the rare pleasant outcome. Pay for it anyway. The red-flag guide covers how to write the ask so it is a repair, not a vibe.

Sewer Line Problems: Bellies, Roots, and the Scope Before You Waive