Drain pasta. Once the pasta is al dente, drain the water and rinse pasta under cold water. Let the pasta drain thoroughly before proceeding to the next step.
Whisk together. While the elbow macaroni is draining combine the mayonnaise, white vinegar, sugar, mustard, and sweet relish in a small bowl and whisk together.
Toss together. Add the cooked macaroni, red onion, red bell pepper, and celery to a large bowl. Pour the mayonnaise mixture over everything and gently toss together until well coated.
Refrigerate and chill. Store in an airtight container in the refrigerator for at least 1 hour to let it chill.
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