Peel potatoes and slice them about a half-inch thick. Then chop each slice into 4 bite-size chunks.
Place potatoes in a pot and cover with water. Boil for 10-12 minutes or until you can pierce them with a fork.
While potatoes are cooking, mix mayonnaise, mustard, sweet pickle relish, salt, and pepper in a bowl and set aside.
Chop the celery and onions.
When potatoes are done, drain them in a colander and let them cool completely.
Mix all ingredients together and toss to coat all potatoes.
Store in the refrigerator in a large glass storage container with a tight-fitting lid.