DayZ field wiki · Survive
Purification tablets
Pond into a maybe
Short answer
Tablets treat water you should not have drunk with your hands. Wells are still better.
Also: water tablets · purify
How it works
Chlorine-style tablets exist. They are not charcoal after the fact. Exact wait times stay empty.
What to do
Bottle, tablet, wait, drink. Prefer the pump.
Don't
Don't tablet the ocean and call it a well — see sea-water.