Add the celery, carrot and onion to the pot and cook, stirring occasionally, until slightly softened, about 5 mins. Add the tomatoes, white beans and their liquid, vegetable stock and water. Bring to a boil and then reduce heat to medium
2 stalks celery, 1 carrot, 1 small onion, 1 450 g can diced tomatoes, 1 450 g can white beans, 2 cups vegetable stock, 2.5 cups water