Cast iron drain pipe in South Florida homes fails from the inside out: corrosion attacks the top of the pipe, erosion wears away the bottom, and in a slab house all of it happens out of sight under the floor. A camera inspection tells you whether the line can be cleaned and lined or has to be replaced, and that single decision moves the cost from a few thousand dollars to well into five figures. Insurance rarely pays for the pipe itself, and Florida courts have been narrowing what it pays around the pipe.
Why cast iron drains fail in Florida homes
Cast iron was the standard drain material in South Florida houses from the 1950s through the late 1970s. In a slab-on-grade home, the main line and most of the branches run in the fill beneath the floor, so the first symptom is often the last stage of the failure.
Two mechanisms work at once. Decomposing waste releases hydrogen sulfide gas, and bacteria living on the damp upper surfaces of the pipe convert it to sulfuric acid. That attacks the crown of horizontal runs, the part of the pipe that is not normally submerged. Meanwhile the bottom of the pipe, the invert, wears down under constant flow until a channel forms along its length. In advanced cases the bottom of the pipe is simply gone, and wastewater is running directly into the soil under the slab.
Industry guides put cast iron’s life expectancy at 50 to 75 years, and some sources cite far more. In practice, many Florida systems are failing decades earlier than that. Our working assumption on any pre-1980 house that has not been repiped is that the drains need to be looked at before anything else is designed.
Signs your cast iron drain is failing
- Slow drains and repeat backups, especially in the lowest fixtures such as a shower or a ground-floor toilet.
- Sewer odor with no visible leak. Corrosion at the crown often shows up as smell before it shows up as water.
- Gurgling in toilets or tubs when another fixture drains.
- Cracked or lifting floor tile, damp baseboards, or a musty smell at floor level.
- Insects or rodents appearing near drains, which can mean an open path through a broken pipe.
- Scale in the cleanout, or a plumber who keeps snaking the same line every few months.
Any one of these justifies a camera inspection.
Camera inspection: what it shows and what to ask for
A sewer camera is pushed through a cleanout or a pulled toilet and records the inside of the line. National cost guides put a residential camera inspection at roughly $250 to $500.
Ask for three things. First, the recorded video, not just a verbal summary. Second, footage counts marked at each defect so the problem can be located on a floor plan. Third, a camera run of the branch lines, not only the main: kitchen, each bathroom and laundry. A main line that looks acceptable says very little about a branch that has been channeling for twenty years.
The defects you are looking for are heavy scale, cracks, holes in the crown, channeling along the invert, offset or separated joints, root intrusion, and bellies. A belly is a section where the pipe has sagged and lost its slope, so waste sits in it permanently. That one matters, because no lining system can fix a belly. The section has to be dug out and re-laid.
Lining vs replacement
Lining, usually cured-in-place pipe, cleans and descales the old line, then installs a resin-saturated liner that hardens into a new pipe inside the old one. It avoids cutting the slab, and on a long main line in a finished house it can be the right answer. Published per-foot figures for trenchless lining sit roughly between $90 and $250 per linear foot, depending on the source and the diameter.
Lining has limits, and they are engineering limits, not sales points. The host pipe has to keep its shape well enough to carry the liner. It cannot correct a belly or a wrong slope. Heavily channeled sections with no bottom left are a poor candidate. Every branch connection has to be reinstated from inside the liner, and the transitions at fittings are where problems tend to appear later. A lining contractor who does not show you the pre-lining video, and the post-lining video, has not finished the job.
Replacement removes the cast iron and installs new PVC at the correct slope. It is the permanent answer and, if the house is being renovated anyway, usually the right one. The question is how you reach the pipe.
Trenching vs tunneling under the slab
Trenching means saw-cutting and breaking out a strip of slab inside the house along the pipe route, replacing the pipe, backfilling, compacting and re-pouring. It is direct, it is visible, and it is noisy and dusty. If the floors are coming up as part of a renovation, trenching is almost always the most economical route, because the floor finish is already budgeted.
Tunneling means digging from outside the house and working under the foundation and slab, leaving the interior floors untouched. It is slower and labor-intensive, but you can often stay in the house, and an expensive floor such as original terrazzo or large-format porcelain survives. Published tunneling rates run roughly $200 to $500 per foot.
From a structural point of view, both methods need care. A trench cut across a slab needs the slab re-tied with dowels and properly compacted fill, or the patch will settle and crack the new floor. A tunnel under a perimeter footing needs to be backfilled and compacted to the same standard as the original, or the footing loses support. In Miami-Dade, a sanitary line replacement is permitted work: the county requires the permit application, its standard slab-cut repair detail, and a special inspector form for the trench backfill and concrete repair.
Typical cost ranges
Costs for this work are hard to compare because published numbers mix outdoor sewer laterals with under-slab drains, and lining with full replacement. The table below shows the figures from national cost guides we reviewed as of 2026. They are national, not Miami-specific, and South Florida labor and access usually push real projects toward the upper end.
| Item | Typical published range | Notes |
|---|---|---|
| Camera inspection | About $250–$500 | Ask for video and branch lines |
| Trenchless lining | About $90–$250 per foot | Not for bellies or pipe with no bottom |
| Under-slab trenching | About $300–$350 per foot added for slab work | Floor finish repair is extra |
| Tunneling | About $200–$500 per foot | Plumbing billed separately in many quotes |
| Tunneling, typical 8–15 ft bathroom run | About $4,500–$7,000 | Plumbing extra |
| Under-slab line replacement, larger runs | Up to about $20,000 | Whole-house systems priced after the camera video |
The arithmetic is what matters. A single bathroom branch might be 10 to 15 feet. A whole-house drain system in a 2,000-square-foot slab home can be well over 60 feet of pipe once the kitchen, laundry and every bathroom are included. At several hundred dollars a foot, that is how full replacements land well into five figures before flooring is put back. Under-slab work in a finished house, especially tunneling to save a terrazzo or large-format floor, is technical work, and it is where we do our best work.
What drives the range: total footage, how many branches tie in, whether floors are being replaced anyway, how deep the line runs, access around the perimeter for tunneling, and whether the main to the street or septic is included. A real number requires a camera video and a site visit.
Will homeowners insurance pay for cast iron pipe replacement?
Generally not for the pipe. Most policies exclude wear, tear, corrosion and deterioration, which is exactly what failing cast iron is. Where there has been coverage, it has usually been for the resulting water damage, and sometimes for the cost of tearing out the floor or slab to reach the pipe.
That access coverage is under pressure. In State Farm Florida Insurance Co. v. Feltes, decided by Florida’s Sixth District Court of Appeal in November 2024, the court reversed a jury award of nearly $60,000 in tear-out costs for a deteriorated cast iron line, holding that the policy’s exclusion for repeated seepage or leakage applied even though the leak was not constant. At least one other Florida appellate court has reversed a homeowner’s jury award on a below-slab cast iron claim.
Read your policy’s water damage section before you file, keep the camera video, and get qualified claims advice. Do not budget around a payout.
When to deal with it
If you are buying, camera the drains during the inspection period. If you are renovating, do it before design is final, because the answer may change where the bathrooms go. If you are already opening the floors, replace the cast iron while the slab is exposed. Doing it later means paying to remove brand-new flooring.
On the Dania Beach house, plumbing was replaced throughout as part of a full gut, which is the cleanest way to solve this problem once. For the full list of what else to check in a house of this age, read renovating an older Florida home. If the drains turn up inside a larger project, our home renovation and bathroom remodeling pages explain how we sequence the work, and whole-home renovation costs covers budgeting.
Frequently asked questions
How long do cast iron drain pipes last in Florida?
Cost guides commonly cite 50 to 75 years, and some sources claim more, but many Florida systems installed between the 1950s and the 1970s are failing well before that. Corrosion from sewer gases and erosion along the bottom of the pipe both progress faster in some conditions than others. A camera inspection is the only reliable way to judge the condition of your specific system.
Is pipe lining as good as replacing cast iron?
It can be, if the existing pipe still holds its shape and slope. Lining creates a new pipe inside the old one without cutting the slab. It cannot fix a belly or a sag, and badly channeled sections with no bottom are poor candidates. Ask to see the camera video before and after lining, and ask how branch connections are reinstated.
Does homeowners insurance cover cast iron pipe replacement in Florida?
Usually not for the pipe itself, because corrosion and deterioration are typically excluded. Some policies have covered resulting water damage or the cost to access the pipe, but recent Florida appellate decisions, including State Farm v. Feltes in 2024, have limited tear-out recoveries. Read your policy and get qualified claims advice before relying on coverage.
Do I need a permit to replace cast iron pipes in Miami-Dade?
Yes. Replacing concealed or defective pipe requires a permit in Miami-Dade, and a sanitary line replacement under the slab comes with specific requirements, including the county’s slab-cut repair detail and a special inspector form covering trench backfill and concrete repair. Clearing a stoppage or repairing a minor leak can be exempt, but replacement is not.
Can I stay in my house during cast iron replacement?
With tunneling, often yes, because the interior floors are not opened. With trenching, it depends on which rooms are affected and how long fixtures are out of service. Bathrooms and the kitchen may be unusable for days at a time. If the work is part of a larger renovation, most owners plan to move out for that phase.
