Combine the water, salt pork, and bacon grease in a large, heavy saucepan. Bring to a boil. Add the beans or peas and return to a boil. Reduce the heat and simmer, covered, until the beans are very tender, about 3 hours. Add more water if necessary to keep the beans or peas covered with liquid.
The pot liquor from purple hull peas is delicious served over slices of white bread.
Makes 4 to 6 servings