Cast Iron Drain Replacement in Knoxville, TN

Cast iron drain replacement in Knoxville, TN swaps corroded or cracked cast iron stacks and building drains for PVC, joined to any sound iron with shielded transition couplings. A camera run decides how much has failed, and a long under-slab run can sometimes be lined from inside instead of dug out.

Updated October 2026

Cast iron drains

How Cast Iron Drains Fail

Cast iron is heavy, quiet and long-lived, but it corrodes from the inside where the water runs. Scale builds up and narrows the pipe, the bottom of horizontal runs thins until it cracks lengthwise, and old lead-and-oakum joints start to weep. Slow drains, sewer smells and stains under a run are the usual signs.

The first step is a camera run through the drains, the same equipment as a sewer camera inspection, to see where the iron is sound and where it's not. Descaling with hydro jetting can buy years on iron that is only scaled; iron cracked through gets replaced.

Cracked cast iron drain replaced with PVC in a Knoxville basement

Planning ranges

What Cast Iron Drain Work Costs Depends On

Cost follows how much iron has failed and where it runs.

Location
Basement and crawlspace runs are easiest; under-slab and in-wall runs cost more.

Length
A single section costs less than a full stack.

Method
Lining avoids trenching but needs round, sound pipe.

Restoration
Drywall, tile or concrete patching afterward.

Permit
A plumbing permit typically runs $100 to $250 where required.

Your options

Replace, Line or Descale?

What the camera finds decides the method.

Option	When it fits	Trade-off
Descale and keep	Scaled but not cracked	Buys time, not a permanent fix
Spot replacement	One cracked section or joint	An opening at that spot
Lining	Long run, round pipe, hard to reach	Needs pipe that holds its shape
Full replacement	Cracks along the run	Most disruption, ends the problem

Cast Iron Stack Replacement

The vertical stack carries every drain in the house down to the building drain and vents it through the roof. A cracked or leaking section is cut out, the pipe above supported with riser clamps so it can't drop, and new PVC fitted with shielded couplings. Where the whole stack has failed, it is replaced floor by floor. Walls are opened only where the stack runs, and the new pipe is tested before they close. Cast iron is quieter than PVC, so insulation around new pipe near bedrooms keeps drain noise down.

Under-Slab Building Drain

The building drain under a slab carries everything out to the sewer lateral, and when it cracks, water and waste soak the soil beneath the floor. A camera finds the failure and a locator marks it on the floor above. A single failed section can be reached through a trench in the slab and replaced; a drain failing along its length may be lined from inside with a cured-in-place liner, avoiding a trench through finished rooms. Either way, the camera runs again after the repair so you can see the result on screen.

Cast Iron to PVC Transition

Where new PVC meets old cast iron, the joint matters. A shielded transition coupling, a stainless band over a rubber sleeve, holds the two pipes in line and seals across their slightly different outside diameters. Unshielded rubber couplings sag under load and are the wrong part below grade. The iron side is cut clean and checked for thickness, because joining new pipe to iron that is about to fail only moves the next leak a few inches along the line.

Scope

What a Cast Iron Replacement Includes

Camera run through stacks and building drain
Failures located and marked
Pipe above supported with riser clamps
Failed iron cut out cleanly
New PVC with shielded transition couplings
Water or air test before walls close
Camera run after the repair

Cast Iron Under Knoxville Slabs and Walls

In Knoxville houses built before plastic drains became standard, cast iron often carries the waste from every bathroom out toward the yard, and much of it sits under slabs and inside finished walls. That makes the camera matter more here than on almost any other drain job. It is the difference between opening one section of floor and opening a whole room, and between replacing the length that failed and replacing iron that still had years in it.

Step by step

How a Cast Iron Drain Job Runs

1
Camera
Drains scoped to find the failed iron.
2
Plan
Replace, line or descale chosen and priced.
3
Support and cut
Pipe above clamped, failed section removed.
4
Replace
New PVC joined with shielded couplings.
5
Test and verify
Drain tested and camera-checked.

Common questions

Cast Iron Drain Replacement Questions From Knoxville Homeowners

How long does cast iron drain pipe last?

Often a long time, but it corrodes from the inside; age and use decide when.

Why is PVC louder than cast iron?

PVC is lighter and carries drain noise more; insulation helps near bedrooms.

Can you replace only part of the cast iron?

Yes, if the rest is sound; the camera tells us.

Do you have to break the slab?

Only for a failed under-slab section that cannot be lined.

Is it messy?

The work stays where the pipe runs, with walls or floor opened only there.

Should cast iron be replaced before a remodel?

If the camera shows problems, yes; open walls make it far cheaper.

Drains & Sewer

Other Drains & Sewer Jobs We Handle

Sewer Camera Inspection

Pre-purchase sewer scope and locate and depth marking.

Sewer Camera Inspection details

Sewer Ejector Pump Service

Basement bathroom ejector and grinder pump.

Sewer Ejector Pump Service details

Sewer Line Replacement

Full lateral replacement and Orangeburg pipe replacement.

Sewer Line Replacement overview

Sewer Cleanout Installation

Two-way outdoor cleanout and indoor cleanout access.

Sewer Cleanout Installation overview

Slow drains or a sewer smell from old cast iron?

Call to get the drains on camera before anything is cut.

Call now (865) 344-9122

Cast iron drain pipe replacement for older Knoxville homes