1. In a large saucepan or a slow-cooker, combine peas, water, celery, carrots, leeks, ham, seasoned salt and pepper.
2. Cover and cook over low heat about 10 hours. If using a saucepan, stir every few hours to keep mixture from sticking.
3. The flavor is even better if you cool the soup, refrigerate it, then reheat the next day.