u/Diligent-Might6031

Just as the title says. When I run hot water in the upstairs bathroom sink, the pipes sound like they’re knocking on the inside of the walls.

Do I need to call a plumber or is this normal? The house was built in 1999 and has had quite a number of “DIY” home “improvements” done by previous owners that are exceptionally questionable.

Thanks so much!