15 to 18 servings
In a six quart pot bring about 5 quarts of water to a rolling boil. Add the pasta and stir until water returns to a hard boil. Boil 8 minutes, or follow package instructions. Drain into a colander and cool by rinsing in cold running water. Set aside.
Mix chopped celery, chopped onion and sweet pickle relish in large bowl. Add the cooled pasta and gently toss to mix. Add mayonnaise to bind. Refrigerate for several hours (or overnight) before serving.