Only about 25% of Americans drink straight tap water.

https://www.ewg.org/news-insights/news-release/2022/05/ewg-f...

That's from a non-representative online poll for people already searching the internet for information about whether or not their tap water was safe to drink.

> Those are findings from a recent survey of 2,800 visitors to EWG’s landmark Tap Water Database, updated in late 2021 [...] Although EWG ran the survey for only a few days, responses came from 2,800 people in about 1,580 unique ZIP codes in all 50 states and D.C., and even some from Canada and Mexico.

Here's an article, also from 2021, based on an academic study which suggests "Nearly 60 million Americans don't drink their tap water", which (US population being 331.9M in 2021) would still leave over 80% who do.

[0] https://theconversation.com/nearly-60-million-americans-dont...