YSK If you ever have to collect water from an outside source (river, stream, lake, etc.), then you should distill the water before drinking it. Boiling is not enough to make it safe!
from /r/YouShouldKnow
YSK 如果您必须从外部水源（河流、溪流、湖泊等）取水，那么您应该在饮用前将水蒸馏。煮沸是不够安全的!