Cast iron sewer pipe

Cast iron was the standard for drainage inside buildings for a long time, and a great deal of it is still in service. What it does over decades is build up scale on the inside and, in places, lose wall thickness.

Those two things look similar on a camera and mean very different things. Scale narrows the pipe and can often be removed. Lost wall is structural and cannot. Almost every disagreement about a cast iron quote is really a disagreement about which one was seen.

What this page cannot establish

SewerOwner cannot tell you what is wrong with your line, and nothing on this page is a diagnosis
the words a contractor uses have no agreed definitions in this trade, and two companies use them differently
no price, range, or cost driver on this site is a quotation, and none can be
nothing here establishes who is responsible for the length of pipe being described
SewerOwner cannot establish how much pipe wall remains anywhere
a rough or dark interior is not by itself evidence that a pipe has failed

Why cleaning before filming changes everything

A cast iron line that has not been cleaned is coated. The camera sees the coating, and the coating looks like damage. Filmed after cleaning, the same line frequently looks unremarkable.

This is not a trick and it is not usually deliberate. It is simply the order the work happens in, and it is the first thing to establish about any footage you are shown.

What is usually being described

scale — build-up on the inside wall, narrowing the bore
corrosion at the bottom of the pipe, where flow sits longest
loss of wall section, sometimes described as channelling
a crack or a hole, which is a different observation again
joints between cast iron and another material, which behave differently

When to act, and when to watch

Wastewater entering the building, a smell that persists after clearing, or repeated backups from the same fixture group are reasons to move. So is any visible leakage inside a wall or under a floor.

A line that drains, has been cleaned, and looks rough on camera is a candidate for documenting and revisiting rather than for immediate replacement. Ask what would need to change for the recommendation to change.

What to ask

Was the line cleaned before it was filmed? If not, can it be, and can we look again?
Is what you are showing me scale, corrosion, or loss of wall?
At what distance, and from which access point?
How much of the run is inside the building and how much is beyond it?
What would reaching this pipe involve — which floors, walls, or fixtures?
Which part of the quoted length have you actually seen?
If we clean and re-inspect rather than replace, what would that cost us in information?

What would change the answer

footage of the internal drain, with distances and an entry point
whether the line was cleaned before it was filmed
whether the observation is scale, corrosion, or loss of pipe wall
which lengths are inside the building and which are beyond it

What to do next

An uncleaned cast iron line photographs far worse than it is, and this is the single most common reason a quote is larger than it needs to be.

Find out whether the line was cleaned before it was filmed

If your situation is different

The work would be inside the building: The main drain running through the building
Replacement has been quoted: Repair or replace
You are weighing two proposals: Compare proposals by stated scope

Cracked pipe
The observation cast iron descriptions most often escalate to.
What drives scope
Work inside a building is priced on access as much as on pipe.
Preparing for replacement
What replacing an internal drain actually involves.
Hydro jetting
The method usually used before a cast iron line can be judged.
Pipe materials
How material shapes the conversation.
Exclusions and assumptions
Internal work is where assumptions hide most easily.
Get help
A person reads it. It is not a contractor booking, and describing what you were told is often enough to work out which question is actually unanswered.