Fish Chowder

2 tablespoons margarine or oil 1 large onion, minced 2 stalks celery, chopped 2 cups tap water 5 medium potatoes, peeled and chopped 1 pound frozen fish fillets 4 or 5 cups milk 1 1/2 teaspoons salt 1/4 teaspoon black pepper 1 cup cold water 1/3 cup flour a jar with a tight fitting lid […]