Web Design
A plumber's website has one real job on most visits: get someone to call, fast. Design decisions should be judged against that, not against how impressive the site looks in a portfolio.
The phone number should be tappable and visible in the header on every page, on both mobile and desktop, not buried in a contact page. A lot of plumbing sites lose calls simply because the number takes too many taps to find.
A visitor with a flooding basement and a visitor planning a water heater upgrade need different experiences. The homepage should route each of them to the right page immediately instead of treating every visitor the same.