Cut any large potatoes in half. In a 3-1/2- or 4-quart slow cooker combine potatoes and green beans. In a medium bowl combine soup, the water, mustard, and dill. Pour soup mixture over vegetables; stir gently to combine.
Cover and cook on low-heat setting for 6 to 8 hours or on high-heat setting for 3 to 4 hours. Stir gently before serving.