Cast-Iron Stack Replacement
Most pre-1950 Charleston buildings drain through cast-iron stacks. Cast iron lasts 75–100 years. If your house was built before 1950 and hasn't had a stack replacement, yours is likely degraded or failing.
What is a cast-iron stack?
The drain stack is the main vertical drain line that carries waste water and sewage down through the building to the municipal sewer connection outside. In historic Charleston buildings, these are typically 4-inch cast-iron pipes, often running inside exterior walls, sometimes through the center of the house.
Cast iron is excellent at sound absorption and durable under normal conditions. But it's vulnerable to rust from the inside (due to acidic waste gases) and from external moisture in Charleston's humid climate. After 75–100 years, the interior surface corrodes, creating rough spots where solids catch, and eventually pinholes develop where water leaks out.
How we diagnose a failing stack
We use CCTV camera inspection (a waterproof camera on a flexible rod) to see inside the pipe. This shows us:
- Rust buildup — reduces capacity and holds solids
- Cracks or breaks — allows sewage to seep into walls and soil
- Offsets or bellies — sections that sag and trap water
- Blockages — mineral buildup, tree roots, or debris
- Venting issues — roof penetrations that are deteriorating or blocked
We'll video your stack as part of our initial survey. That footage tells us whether repair (hydro-jetting, spot relining) makes sense, or whether full replacement is necessary. We share the footage with you and any architect on the project so everyone understands what's happening.
The replacement process
Survey & design (3–5 days)
We inspect the stack from roof to basement, measure wall thickness, identify routing through floors, and assess what access cuts are needed. We coordinate with any architect to determine the least-disruptive path.
BAR submission (if exterior work, 2–4 weeks)
If the stack runs up an exterior wall, we may need Board of Architectural Review approval for exterior scaffolding or roof-level work. Interior stacks rarely need ARB sign-off, but we always check.
Material prep (1 week before work)
We determine the replacement material (cast iron, PVC, or ABS depending on code and your preference), arrange for plumbing permits, and coordinate with masons or plasterers who may be needed for wall patching.
Demolition & replacement (2–4 weeks)
We cut the old stack into manageable sections, remove them carefully, and install the new stack section by section. We support the new pipe to prevent sagging, vent it properly per IPC (International Plumbing Code), and test the whole system before we close walls back up.
Testing & closeout (1 week)
We perform smoke tests and dye tests to ensure all connections are tight, no leaks are present, and venting is correct. We pull permits, get inspections signed off by the city, and patch/paint all wall openings.
Material selection
| Material | Pros | Cons |
|---|---|---|
| Cast Iron | Durable (75–100 yrs), sound-dampening, historic authenticity | Heavy, requires lead-safe removal, more labor |
| PVC (Schedule 40) | Lightweight, quick installation, modern reliability | Less sound dampening, less historic feel, can require ARB discussion |
| ABS | Similar to PVC, slightly better for venting transitions | Rare in the Southeast, harder to source |
Most of our recent replacements use PVC for simplicity and code compliance. If the stack is visible and you want to preserve the original material character, we can use cast iron—it will last another 75–100 years. The choice is yours; we explain the cost and timeline for each.
Cost & timeline
Typical stack replacement: $8,000–$18,000 depending on stack height, number of story levels, wall thickness, and whether the stack is interior or exterior. A three-story exterior stack takes longer than a three-story interior one.
Timeline: 6–10 weeks from initial survey to final inspection, including BAR review if needed. The actual work (demolition and installation) takes 2–4 weeks. The rest is coordination, permitting, and waiting for city inspections.
Next steps
If you suspect a failing cast-iron stack—frequent backups, slow drains, musty smells in the basement, or water staining on exterior walls—schedule a site visit. We'll inspect the stack, show you video of what's happening, and give you an honest estimate of what replacement requires.
Schedule a survey →