In a large pot over high heat, combine the potatoes, carrot, turnip, onion, garlic, chicken and water to cover. Bring to a boil and reduce heat to low. Let soup simmer for 45 minutes to 1 hour. Skim fat, if desired, and season with salt and pepper to taste.
Remove chicken leg from the soup and allow it cool. Remove the meat, returning it to the soup, and discard the skin and bones. Simmer for 30 to 45 more minutes, or longer, if desired.