My usual measure at camp is a capful per every three gallons. I used this water mainly for dishwashing as a disnfectant after the soap and scrub. I also used this solution in spray form to disinfect tabletops and working surfaces. I think that may be a little strong for drinking water. I can't remember what the dept of health requirement was, but I know mine was a little higher than theirs.
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)