What quantity should be used to maintain 1.0 ppm chlorine residuals in 1000,000 gallons of potable water tank?

Hi, ahmeia0a!

Is this a homework question, please?

Thanks!

1.0 ppm is 1 mg in one litre.

Convert the amount of gallons into litres.
In each litre, there is 1 mg. How many grams would there be in the amount of litres you just obtained above?