Service line material can be verified by viewing the water line at the point where it connects to the meter (usually outside in a boxed pit) and where it enters the home (usually in the basement or foundation crawl spaces). NPR has developed an interactive plumbing identification guide:
https://apps.npr.org/find-lead-pipes-in-your-home/en/ and there is a representative pictorial example of types of plumbing materials included below.