Cook potatoes in boiling salted water for 25-30 minutes, or until tender. Peel and slice potatoes. In large skillet, cook bacon till crisp; drain and crumble, reserving 1/4 cup drippings. Cook onion in reserved drippings till tender but not brown. Stir in flour, sugar, salt, celery seed, and pepper. Add water and vinegar. Cook and stir till thickened and bubbly. Cook and stir 1 - 2 minutes more. Stir in bacon and potatoes. Cook 5 minutes or till heated through. Add hard-cooked eggs and toss lightly. Refrigerate overnight. Reheat just before serving.