Part of my line is iron and part is PVC from an old repair. Does all of it have to go?

Not always. This Old House lists limited corrosion spots and single connection problems among the jobs a targeted repair can handle, and says replacement makes more sense when the problems are widespread or come from aging material. The camera video decides it: ask for footage marks at every rusted or cracked spot so you can see whether the remaining iron is sound.

Is new cast iron worth paying for when PVC is so much cheaper?

Sometimes. Cast iron costs several times more than PVC for the pipe alone, and This Old House says buyers choose it where extra durability or sound dampening matters. Both are on the 2021 plumbing code's list for building sewers. Mobile's code leaves ABS off that list, so ABS isn't an option for the yard run.

What should hold the joint where new plastic meets my old iron?

The 2021 plumbing code Mobile uses says a joint between plastic pipe and cast-iron hub pipe has to be a caulked joint or a mechanical compression joint, and joints between different materials have to use couplings made to set ASTM standards. Ask the plumber which coupling the quote includes and whether it has a metal shield.

Does iron pipe have to be dug out, or can it be burst in place?

Bob Vila's guide says nearly all common pipe materials can be replaced by pipe bursting, whatever their condition. A stretch that has collapsed is the exception: cost guides say trenchless methods aren't suited to collapsed pipe, so that part is usually dug and replaced.

Cast Iron Sewer Pipe Replacement in Mobile, AL

Typical cost of pipe: This Old House puts materials for a 40-foot run at $800 to $3,000 in cast iron against $120 to $320 in PVC, before labor.
Timeline: swapping out iron runs about 1 to 5 days on the national guides' numbers (what sets the length).
Lifespan: This Old House gives cast iron 75 to 100 years with proper care; HomeGuide gives 50 to 100.
MAWSS's view: old cast iron laterals, like clay and concrete ones, have "deteriorated over time" and "often need full replacement".

Mobile Sewer Line Replacement sends your details about a rusted iron line to a plumber who can quote replacing it. Iron sewer pipe fails through corrosion, cracks and worn joints. The fix can be one coupled section, a lined or burst run, or a full replacement in PVC or new cast iron.

Cast Iron Sewer Pipe Problems and How Each Is Repaired

Iron sewer pipe loses metal as it corrodes, and over time that weakens the wall, opens cracks and loosens joints. The camera shows how much of the run is affected. That matters more to the bill than the pipe does: This Old House says labor and excavation usually make up the largest share of the price.

Old cast iron sewer pipe section cut lengthwise on a workbench, its inside crusted with lumpy brown rust that narrows the opening

Corrosion and Scale Inside the Pipe

Cast iron corrodes on both its inner and outer surfaces. An encyclopedia entry, writing mainly about water pipe, says the buildup inside can narrow the bore, and that as more iron is lost the pipe's structure weakens. In sanitary sewers, hydrogen sulfide gas from the waste adds acid corrosion that is worst along the top of the pipe. A few rusted spots on otherwise sound pipe can be repaired; corrosion along the whole run points to replacing it.

Cracks Along the Pipe

A crack is an opening roots and soil can use: MAWSS warns that roots find even the tiniest crack in a lateral, and that defective laterals can draw in enough soil to open holes in the yard. MAWSS's lateral diagram lists "breaks, cracks, holes" among the defects its tests find. One cracked length in good pipe can be cut out and replaced; Bob Vila's guide puts the average cracked-pipe repair at $1,050. See sewer line spot repair for the methods.

Section of old black cast iron sewer pipe joined to new white PVC pipe with a stainless steel shielded rubber coupling in an open pit

Failed Hub Joints and Iron-to-PVC Transitions

Cast iron sewer pipe comes as hub-and-spigot pipe or hubless pipe, and a repair or partial replacement always ends at a joint between old iron and new pipe. The 2021 plumbing code allows plastic-to-iron hub joints only as a caulked joint or a mechanical compression joint, and couplings for hubless iron need a rubber sleeve inside a metal shield. Ask which coupling the quote uses at each end of the new pipe.

Iron Under the House and Iron in the Yard

Cast iron under a slab is covered on under-slab sewer line replacement. In a crawl space the pipe hangs in the open, and the code limits hangers on cast iron to every 5 feet (10 feet where 10-foot lengths are used). The yard run out to the property line or curb is the owner's private lateral.

Replacing Cast Iron in Kind or in PVC

Both cast iron and PVC sewer pipe are on the code's approved list. This Old House gives PVC more than 100 years and says buyers pick iron for durability or quiet. On price the gap is wide: Bob Vila puts pipe for 48 feet at $1,104 to $3,600 in iron against $73 to $376 in PVC. Whether a trenchless method suits a given iron run is a question for the camera video; see pipe bursting for the code's limits.

Gloved hands holding a sewer camera monitor showing a cracked clay pipe joint with roots, beside an open cleanout in a lawn

Why Mobile homeowners, landlords and businesses call Mobile Sewer Line Replacement

One licensed plumber gets the request, not a bidding list
No charge to you for the introduction
Ask to keep the camera video from before and after
Alabama plumbing licenses can be checked online

What Changes the Price of a Cast Iron Sewer Job

How much of the run is bad
HomeGuide says partial repairs often cover 1 to 15 feet, while a full line is usually around 40.
Where the iron is
Pipe under a slab costs far more to reach than pipe in open yard; under-slab sewer line replacement has those figures.
The new material
Choosing cast iron again multiplies the pipe cost several times over PVC.
Concrete on top
Bob Vila averages $1,750 to repair a driveway and $1,400 for a patio or walkway after sewer work.

Ask for a written quote that lists the footage being replaced, the pipe type and the couplings at each end, and keep the camera video so you can compare bids on the same defects.