1. Cook the bacon pieces in a heavy soup pot until they start to brown. Add the onion and celery and cook until just soft.
2. Sprinkle on the flour and cook for 3 minutes. Add the water and broth. Add the potatoes and slowly bring to a boil. Reduce the heat and simmer until the potatoes are soft (about 30-40 minutes).
3. In a separate bowl, ladle in 2 cups of the soup broth. Whisk in the sour cream until blended. Whisk the mixture back into the soup. Heat for 3 minutes longer. Adjust seasonings. Serve warm. (Re-heat any leftovers slowly).