For a turkey up to 20lbs, in a large pot over high heat, combine 1 gallon of water and brine. Bring to a boil and stir to dissolve. When dissolved, let cool. In a 5-gallon container, place 1.5 gallons of ice water followed by the thawed turkey. Top with cooled solution and refrigerate for 12 to 36 hours. Turning once half way through. When ready to roast, remove turkey from solution, rinse throughly and pat dry. Cook as directed.