Recently, I watched a video that compared cultural beliefs between black and white british people. Of note, was that black people didn't drink tap water whilst white people did. I would assume this is due to historical reasons, black people were more likely to come from countries with worse health standards where this advice would make sense, and maintained this belief when they moved over to Britain.

Now that I've lived in an older home, I think this belief makes more sense. Whilst the water is safe, pipes in older homes tend to impart a taste to water due to leeching. Given black people are on average poorer, and likely to live in older homes, their tap water would taste different due to older pipes. This would make the suspicion of tap water more reasonable. It is partly caused by a genuine difference from socioeconomic factors, rather than only cultural factors. It seems that this happens quite frequently. A belief sounds unreasonable because it contradicts a fact, only for more information to reveal that there is no contradiction.