With a fork, mix together the flour, sugar, and salt. Cut in the Crisco with a pastry blender until the mixture is crumbly. Beat together the vinegar, egg and water.
Combine both mixtures, and stir until moistened. If the dough is still dry, add more ice water a teaspoon at a time as needed to get the right consistency. Mold the dough gently into a round and refrigerate for at least 1 hour.
Separate the dough into 5 portions. You should have enough dough to make 2 8-9" double crust pies and one 8-9" single crust pie.
Why would you need more water? It all depends on the temperature and humidty inside your kitchen as well as how you measure your flour.