What an Older House Adds

On a recent build, "not required to inspect concealed piping" costs you very little: the material is documented and uniform. On an older house it is the main question, because what is behind the wall may not be what is under the sink.

ASHI asks for the predominant material to be described, which is an accurate word for a house that has been altered several times and not a complete answer about any one run.

Source: ASHI Standard of Practice.

InterNACHI lists polybutylene piping among the things an inspector is not required to inspect. On a house of the right age, whether any is present is a real question with real consequences, and the standard does not oblige anyone to answer it.

If it matters to you, it has to be asked for specifically. It will not arrive in the report by default.

Source: InterNACHI Home Inspection Standards of Practice.

The older the house, the more likely the original line out to the street is still there, and both standards put it outside the inspection. That is the case for a separate survey, and it strengthens with every decade.

Source: InterNACHI Home Inspection Standards of Practice; ASHI Standard of Practice.

Plenty of old houses have been fully re-piped and plenty of newer ones have been altered badly. Age changes the odds and the questions worth asking. It does not decide what is in the walls, and anyone who tells you it does is guessing with more confidence than the data allows.