Sprinkle gelatin over water in small saucepan. Let stand 1 minute. Cook and stir on low heat until gelatin dissolves.
Combine pumpkin, sweetened condensed milk and pumpkin pie spice with wire whisk until well blended. Stir in gelatin mixture. Let cool 10 minutes. Gently stir in whipped cream.
Pour mixture into crust. Chill at least 3 hours, or until set.