The original pipes here in The Boonies were wood. The last of them were replaced not all that many years ago. These appear to be hollowed-out logs. The ones here were built by barrel makers, so, long staves and held together by rings. In the frontier era here, wood was used for everything — roads, construction, heating, cooking, even the steam trains.
They were made using a long auger and inside and outside tapering gouges.
The process is still demonstrated at a festival in St. Johnsbury, Vermont.
The Romans may have had the technology, it is pretty simple.
It was about 48" in diameter...banded as you said. The wood swells when wet and makes a tight seal. It was easier and cheaper to replace with wood. One great job.
I wonder what kind of wood those pipes were made of, that they lasted for a millennium. The Romans, for as brutal as they were, were master builders and engineers.
In the midwest we had orangeburge. Rolls of tar paper like piping I believe taped together.