Obtain a clean one gallon jug. Dissolve the 500 grams of Sodium Thiosulfate in a large pitcher of lukewarm tap water. Stir until all the crystals are dissolved. Then transfer the solution with a funnel to the gallon jug. Top off the jug to make a full gallon of stock solution.
•Add 2 drops of the stock solution per 1 gallon of the water to be treated.
•One gallon can treat 37,850 gallons or more. Over-dosage is virtually impossible.