Cast Iron Sewer Replacement
An independent, licensed plumbing contractor. Not affiliated with Denver Water or the City and County of Denver.
Cast iron was the standard for Denver building drains and stacks for decades. It corrodes from the inside out, builds heavy scale, and eventually channels along the bottom until the pipe floor is gone.
- Grey black metal wall with rust nodules.
- Scale buildup narrows the bore.
- Channeling wears the pipe floor away.
- Descaling and lining can extend service life.
- Replacement once the invert is gone.
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What Cast Iron Sewer Pipe Is
Cast iron is heavy grey metal pipe joined with lead and oakum or with rubber couplings on later work. It was used for building drains, stacks, and underslab lines in Denver from the early 1900s into the 1970s.
On camera it reads dark grey to black with rough rust colored nodules and a rippled surface. A magnet sticks to it where the pipe is accessible, which is the fastest confirmation above ground.
Cast iron often lasts 50 to 80 years, but the last decade of that life is usually rough: repeated blockages, slow drains, and sewer odor.
(720) 935-6221How to Recognize Cast Iron
- Magnetic where exposed in a basement or crawlspace.
- Heavy rust flaking and tuberculation on camera.
- Rough interior that snags a camera head.
- Hub joints sealed with lead.
- Bore visibly narrowed by scale.
How We Diagnose It
Why Cast Iron Fails
Wastewater is mildly corrosive and sits longest at the bottom of the pipe. Over decades that thins the invert, the floor of the pipe, faster than the crown. The result is channeling, a groove worn through the bottom while the top still looks intact.
Scale grows inward at the same time. Tuberculation reduces effective diameter, catches paper and grease, and turns a full size line into one that blocks constantly.
Once the invert is perforated, soil enters, bedding washes out, and sections drop. At that point there is no wall left to line against.
Options From Cleaning Through Replacement
- Descaling and hydro jetting to recover diameter when the wall is still sound.
- Pipe reaming to cut the bore back to full size before lining.
- CIPP lining when the pipe holds shape and the invert is intact.
- Open cut replacement for underslab runs with channeling or breaks.
- Pipe bursting for buried yard runs where a trench is undesirable.
How a Cast Iron Project Runs
- 1
Inspect Before Cleaning
We camera the line first so we know whether the wall can survive descaling.
- 2
Descale and Re-Inspect
Scale is removed and the line is re-inspected, because the real wall condition is only visible once the buildup is gone.
- 3
Decide Line or Replace
Sound wall with a good invert can be lined. Channeling or perforation means replacement.
- 4
Execute and Verify
The chosen work is completed and confirmed on camera before the site is restored.
Get a Straight Answer on What Your Line Needs
What Drives Cast Iron Cost
Location dominates. A yard run is straightforward. An underslab run inside a finished basement adds concrete cutting, dust control, and floor restoration.
Scale severity affects cleaning time, and cleaning time affects whether lining is even worth pricing.
Length, number of fittings, and stack tie-ins all add labor on interior work.
- Iron near the building meeting clay in the yard is a recurring defect point on park edge apartment properties, covered on our Cheesman Park page
- The same two material run turns up under the bungalow blocks described on our Platt Park page
Frequently Asked Questions
Applicable Methods and Related Diagnosis Pages
Hydro Jetting and Descaling
High pressure water and cutting heads that strip grease, roots, and scale.
Explore Hydro Jetting and DescalingPipe Reaming
Cutting the interior of a pipe back to full diameter before lining or cleaning.
Explore Pipe ReamingCIPP Cured-In-Place Lining
A resin liner cured inside the host pipe to form a new jointless pipe wall.
Explore CIPP Cured-In-Place LiningOpen Cut Excavation
Traditional trenching when the line has to be exposed and physically replaced.
Explore Open Cut ExcavationRepair or Replace: How to Decide
The evidence that separates a fixable defect from a line at end of life.
Explore Repair or Replace: How to DecideSewer Line Lifespan by Material
Expected service life for every material buried under Denver properties.
Explore Sewer Line Lifespan by MaterialFind Out If Your Cast Iron Can Still Be Saved
The invert condition decides between descaling, lining, and replacement.