Mix 1 pound hamburger with 3/4 cup grated carrots and 3/4 cup grated potatoes. Add 1 egg and 1 small onion chopped fine and 1 teaspoon salt. Roll into 15 balls. Fry and brown evenly turning often. Place in bottom of casserole dish. Mix 1 can cream of mushroom soup with 1/2 soup can of canned milk and 1/2 can water. Pour this sauce over the meatballs and bake 350 degrees 30 to 40 minutes. Baste the meatballs several times during baking time.