You can find orange-flower water in the spice section or at natural or ethnic-food stores.
Bring 2 1/2 cups water and salt to a boil in a large saucepan. Add rice; cover, reduce heat, and simmer 20 minutes. Remove from heat; let stand 10 minutes.
Stir in the milk, sugar, and 1/2 teaspoon cardamom. Bring to a boil; reduce heat, and simmer, stirring frequently, 20 minutes or until rice is tender and the mixture is thick and creamy. Place in a large bowl; cool to room temperature, stirring occasionally. Stir in remaining 1/4 teaspoon cardamom and flower water. Chill 4 hours. Sprinkle with pistachios.