Cast iron pipes in older Houston homes: when to replace

Cast iron was used as drainage pipe through the twentieth century, and HomeGuide notes it is no longer commonly used for sewer lines because it tends to rust. Houston has a lot of housing from that era. Census Bureau survey data for 2020 to 2024 show about 1.04 million housing units in the City of Houston, with a median year built of 1982 (ACS tables B25034 and B25035):

The age of a house is only a clue. Some older homes have already been partly repiped, and the only way to know what is under your slab is to look at exposed pipe at the cleanout, water heater closet or under sinks, and to run a camera through the line. Suburbs vary widely: about 57 percent of homes in Pasadena predate 1980, compared with about 11 percent in Pearland.

HomeGuide's 2026 sewer line guide lists a typical lifespan of 50 to 100 years for cast iron sewer pipe, the same range it gives PVC, and 30 to 60 years for clay and Orangeburg pipe. It also says cast iron is no longer commonly used because it tends to rust. That wide range is the point: some 1960s cast iron is still sound, and some has failed. Corrosion is the main mechanism. In sewers, acidic gases such as hydrogen sulfide produced by microbes can corrode internal pipe walls, according to the Wikipedia article on cast iron pipe, and buildup inside the pipe narrows it over time.

• Drains that clog again soon after being cleared, or several drains backing up at once.
• Sewer odors inside the house, or gurgling drains.
• Unexplained damp spots, floor cracks or a rise in water bills in slab homes, which can also point to a supply leak.
• Rust-colored flakes or scale in the debris a plumber pulls out during cleaning.

HomeGuide lists odors, gurgling, clogged drains, debris and puddles as signs of a failing sewer line, and HomeAdvisor's 2026 sewer repair guide adds recurring backups and sulfur smells.

Start with a camera inspection. HomeAdvisor's 2026 sewer inspection guide puts the national average at $995, with a typical range of $271 to $1,725; HomeGuide's drain cleaning guide lists $125 to $500. Ask for the video file and the footage locations, then decide among these options, with national costs from HomeAdvisor's and HomeGuide's 2026 guides:

HomeAdvisor notes that trenchless methods are not an option when a pipe has fully collapsed, and it lists cast iron as a material at $50 per linear foot compared with $4.50 for PVC. HomeGuide puts a full replacement of a 40-foot sewer line at $2,000 to $10,000. Drains under a slab cost more than an exterior sewer line because they require tunneling or cutting the floor; see our slab leak guide for those methods.

Inside the City of Houston, the Permitting Center's Plumbing Inspection section handles plumbing permits and sewer inspections. Suburbs have their own rules; Sugar Land, for example, lists exterior sewer line repair and drain pipe repair under the home as permitted work. A licensed plumber should pull the permit. Check the license in the Texas plumbing license search before work starts.

1. Can I see the camera footage of every section you want to replace?
2. Which sections are cast iron, and which are already plastic?
3. Is the price for the exterior sewer line, the under-slab drains, or both?
4. Who restores the floor, flooring and landscaping, and is that in the price?

Our sewer line repair guide and cost guide cover the rest.

We are an independent guide, not a contractor, and we do not perform plumbing work or answer phones. To reach a plumber, call one of the licensed contractors listed on this page or see all listed contractors. Questions about this guide: email us. We do not take service requests. Check the license of anyone you hire, including the contractors listed on this page.