Cut the fatback into 1/4-inch cubes and put it into a 6 to 8 quart Dutch oven. Add the water. Put in the oven, uncovered and stir every 30 to 40 minutes, pressing the pieces against the pan in order to help them melt. Cook until the fat has melted, the water has evaporated and the pieces begin to brown slightly, approximately 3 to 4 hours. Pour through a fine mesh strainer into a heatproof container and allow the fat to cool completely before covering and storing in the refrigerator.