I used to live in Warsaw. I had no clue that clams tested the water that I drank, thank you clams for your service.,(reply>), @clray123 Is 40 years old?,(reply>), @TheBlacktom The case may be that old people continued to boil their water even though it no longer was necessary. Thus also giving a bad example to younger people.,(reply>)," @Kamila K. Hardened and nitrate<br> water is full of chemicals. Harmful to health. That's why people boil the water or use filter . Although sulphate chloride  carbonate and unknown salts. Can't do much damage but still not healthy.",(reply>), @Retro Game Elements no it’s not considered unsafe to drink. Don’t spread bs.,(reply>), @wojtekpolska I live in a small town in the south (Lesser Poland). I remember similar campaign encouraging to drink tap water taking place at least couple years ago. Tap water was probably completely safe to drink a long time ago - maybe it's one of the stereotypes derving from the communism period (don't drink tap water) that is no longer valid. Although tap water in my region is quite stony, so ppl are using water filters anyway.