In a 3-quart dutch oven fry bacon until crisp and crumbles easily. (Remove bacon and set aside). Saute onion in bacon fat until tender. Add water, clam juice, potatoes and cook until potatoes are tender. (Do not drain). Add heavy cream, half-and-half and milk stirring frequently so it doesn't scorch. Heat to steaming (do not boil). Add clams w/juice, crab, bacon, butter, salt and pepper and cook for 5 minutes more stirring frequently. To Reheat: Only reheat as much as you can eat. Don't reheat the whole pot.