Clay country
The tract belt of the 1950s through the early 1970s — Cambrian, Blossom Valley, Berryessa, the older parts of Evergreen and Almaden, plus the pre-war streets of Naglee Park, the Rose Garden and Willow Glen — is largely vitrified clay: rigid, durable, and jointed every few feet. Clay does not corrode; it separates and admits roots, which is why this belt produces the seasonal, repeating backup rather than the sudden one.
Where Orangeburg turns up
Scattered through post-war construction is bituminous fiber pipe, sold as Orangeburg. It deforms under load with age — oval, then flat — and no amount of clearing reverses that. When a camera finds it, the conversation is replacement, and it is worth knowing before paying for a third clearing.
The newer blocks
Silver Creek, Santa Teresa, the later phases of Almaden and Evergreen, North San José infill: ABS and PVC, glued rather than jointed, and largely uneventful. When these lines back up it is usually something introduced — wipes, grease, a construction blockage — rather than the pipe failing.
Who is responsible where
This is where the towns stop matching each other.
In San José, the lateral is the owner's, with the City maintaining the lower section from an approved property-line cleanout to the main as a courtesy where that cleanout exists.
In Campbell, Los Gatos, Monte Sereno and much of Saratoga, sewers are run not by the towns but by the West Valley Sanitation District, which owns and maintains hundreds of miles of mains and lower laterals across its area. The starting position for a homeowner there is materially different from the one three miles away in San José.
Elsewhere — Santa Clara, Sunnyvale, Milpitas, Cupertino — the operator may be the city or a separate sanitary district, and the split between "yours" and "theirs" is theirs to define. The bill that arrives for sewer service names the agency; that is the fastest way to find out who to ask.
County pockets
Burbank, the Cambrian Park pocket, Fruitdale and parts of East Foothills and Alum Rock carry San José addresses but sit outside the city. Plumbing permits for those parcels are the County of Santa Clara's, on the County's schedule. The County's Property Explorer answers it for a specific address in a couple of minutes.
Why the list is drawn this way
Because the answer to «who pays for the pipe under the street» changes at the town line, and an estimate that ignores that is worth nothing. Every address above gets checked against its own agency, its own permit desk and its own version of the cleanout question. No trucks are implied by any of it — this business is pictures in, writing out.
Agency and responsibility statements are drawn from published City of San José sewer guidance and from West Valley Sanitation District's own published description of its system. Both can change, and neither is a substitute for asking the agency that bills you.