How to tell what your sewer pipe is made of

Updated October 30, 2026 · 3-minute read · Old House Sewer Lines

To find your sewer pipe material, start where the main drain leaves the basement wall, then confirm the buried section with a sewer camera. In older houses the answer is often clay or cast iron, and the material can change partway to the street.

Clay and cast iron are the two materials FEMA's homeowner flooding guide names for the laterals of many older houses (FEMA, Urban Flooding guide). Lines that have been replaced may be PVC or another plastic, and some laterals elsewhere in the country were laid in tar-paper Orangeburg pipe; its use in Westchester is not documented in a primary source. Knowing which one you have shapes what can be done when the line fails.

Start in the basement

What you can see indoors is the building drain. Under the residential code wording the Department of State quotes, that drain reaches two and a half feet of pipe length outside the foundation, and only then does the building sewer begin its run to the public main (NYS DOS, Building Traps). So the pipe at the wall is a strong clue but not proof of what lies under the yard.

Cast iron is the easiest to spot. Hub-and-spigot pipe has a flared bell at each joint, and older joints were sealed with oakum and poured lead; no-hub cast iron is joined with a gasket and a stainless steel band clamped over plain ends (CISPI handbook). PVC is made to different ASTM standards for sewer pipe (D3034) and drain pipe (D2665), and the difference is explained in SDR 35 vs Schedule 40.

Older drains may also pass through a house trap, a fitting New York no longer allows in new work. State guidance says an old trap may double as the sole access point at the drain-to-sewer junction, which makes it one of the few ways into the line.

Confirm with a camera

The buried lateral can only be seen from inside. NASSCO, the trade body that writes the standard defect codes used in sewer video reports, specifies a color camera that can pan and tilt, or a panoramic side-wall scanner, and video covering the pipe's whole circumference (NASSCO CCTV specification). NASSCO's PACP system gives operators a standard way to code what they see, with separate sections for structural and maintenance defects. A pipe that has flattened out of round is the failure the City of Tempe, Arizona, describes for Orangeburg (Tempe handout, archived).

Ask the operator to state the material at each change and the footage where it changes. A lateral can mix materials, for example clay sewer pipe joined to a plastic section, so one look at the wall is not enough. More on what to expect from the video is in sewer camera inspection and reading a sewer inspection report.

Why it matters

Material decides which repairs are on the table. Orangeburg can be too weak to survive the jet cleaning that precedes lining, according to Fairfax, Virginia. For clay, the industry itself flags field-made joints on runs past 70 years (NCPI FAQ). Cast iron and PVC are both on New York's approved list for new building sewers; bituminous fiber is not. Background on each is in Orangeburg pipe and cast iron sewer pipe.

Key facts

Older-home laterals are commonly clay or cast iron, FEMA says (FEMA).
The building drain ends 30 inches of pipe outside the wall, where the building sewer starts (NYS DOS).
Hub-and-spigot cast iron has bell ends; no-hub cast iron uses clamped gasket couplings (CISPI).
NASSCO's video spec calls for pan-and-tilt or side-scanning cameras showing the whole pipe wall.
An old house trap can be the only access point at the junction with the sewer, per NYS DOS.