Old Sewer Pipe Materials: Clay, Cast Iron, Orangeburg and Plastic

How to tell what you have

Start where the pipe is visible: where the sewer leaves the house in a basement or crawlspace, or at a cleanout. Don't assume the buried line matches what you see. Ann Arbor, Michigan's building department notes that in most houses there with fiber pipe, it probably started about 5 feet outside the foundation and ran to the street, while a different material was usually used under the basement slab (City of Ann Arbor).

Plastic is the easiest to recognize. In one manufacturer's product line, ABS drain pipe is black, PVC drain-waste-vent pipe is white, and PVC sewer pipe made to ASTM D3034 is green or white (Charlotte Pipe). The ASTM specifications for PVC sewer pipe and PVC drain pipe include a form of marking, so an exposed piece may be printed with the standard it meets (ASTM D3034, ASTM D2665).

For buried pipe, Ann Arbor's guidance lists three ways to find out: a video scan, which may show damage patterns typical of a material; a cable machine, which sometimes brings back pieces of pipe but may damage it further; and digging down to the pipe, which gives a positive answer but tears up the yard. What a sewer camera inspection shows explains what to ask for.

Vitrified clay pipe

Clay pipe has served U.S. sewers for more than 200 years, and on older lines the joints are where trouble tends to start. The National Clay Pipe Institute, the clay pipe industry's trade group, says clay pipe made in the U.S. since the 1950s has factory-applied, flexible compression joints, but installations more than 70 years old may have joints made in the field that don't meet current standards. It adds that clay pipe made before the 1950s may not be fully vitrified and may have laminations, both of which lower its strength (NCPI).

Older joints are where roots get in. Traverse City, Michigan's sewer department says roots follow water vapor escaping from cracks and loose joints, and that clay tile pipe installed there was easily penetrated and damaged by roots (City of Traverse City). If your clay line keeps clogging, see tree roots in sewer lines.

Cast iron pipe

Cast iron soil pipe comes in two main types: hub-and-spigot pipe made to ASTM A74, with joints sealed by a rubber compression gasket or by lead and oakum, and hubless pipe joined with couplings (CISPI handbook).

Corrosion is the main thing to watch for. The Cast Iron Soil Pipe Institute, the manufacturers' group, says most U.S. soils aren't corrosive to cast iron, but soils heavy in decomposing organic matter, alkalis or salt, such as tidal marshes, and fill made from industrial or municipal waste can be. Inside the pipe, strong acids or other aggressive chemicals with a pH of 4.3 or lower can corrode cast iron if they stay in contact for long periods (CISPI handbook). That's one more reason to be careful with acid drain openers; see chemical drain cleaner safety.

Orangeburg (bituminized fiber) pipe

"Orangeburg" was a brand name that became shorthand for bituminized fiber pipe. Ann Arbor's building department describes it as plant fibers and asbestos soaked in a tar-like binder, a product that spread during and after World War II, when metal was scarce. In Ann Arbor it was used from roughly the early 1950s to the early 1970s, and the city dropped it from its approved materials in 1970 (City of Ann Arbor). Dates elsewhere vary, so only an inspection can tell you whether your line has it.

Ann Arbor lists how it fails:

• The bedding shifts and the pipe pulls apart, usually at the joints.
• Roots invade the joints and break sections apart.
• The material deteriorates and flattens under the weight of the soil, losing the round shape it needs to drain.
• Solvents, paint thinner and similar chemicals poured down drains attack the tar binder, and the pipe can rot from the inside out.

The city also warns that clearing it with a cutting head can damage it further and may only buy time, and that in many cases replacement is the only workable fix. Because the material contains asbestos, ask any contractor who will dig it up how they'll handle and dispose of the old pipe.

ABS and PVC plastic pipe

Plastic sewer and drain pipe is made to ASTM specifications. D2661 covers ABS Schedule 40 drain, waste and vent pipe (ASTM D2661). D2665 covers PVC drain, waste and vent pipe (ASTM D2665). D3034 covers Type PSM PVC sewer pipe and fittings and says they should be installed according to ASTM D2321, a separate installation practice (ASTM D3034). One manufacturer notes that ABS is more common in the western U.S. (Charlotte Pipe).

Plastic's main advantage underground is fewer, tighter joints. Traverse City's sewer department says PVC resists root intrusion better than clay because it usually has fewer joints, and its tight joints are less likely to leak when the backfill around them settles (City of Traverse City). That doesn't make plastic trouble-free, so a camera is still the way to check its condition.

What the material means for cleaning and repair

Before any cleaning, tell the technician what you know about the pipe and ask whether a camera look should come first on old or fragile pipe. Drain cleaning methods explained compares the tools.

For repairs, the material and its condition decide what's possible. For failed Orangeburg, Ann Arbor notes that pipe bursting, which replaces the pipe without digging the entire line, may spare landscaping but needs large holes at each end (City of Ann Arbor). Sewer line repair options explains the code limits on lining and bursting.

Bottom line

Your pipe's material is a clue, not a verdict. Figure out what you have from the visible pipe, any records and a camera inspection, then let the video of your line's actual condition drive the cleaning and repair decision. This guide is general information, not professional advice; a licensed plumber who has inspected your line on camera can tell you what it needs.