Place the potatoes in a large pot of water. Bring to a boil and boil for about 15 minutes, until just tender when pierced with a knife. Keep a close eye on the potatoes, as you don't want to overcook them. Drain the potatoes and place in the refrigerator for several hours to cool. While the potatoes are cooling, prepare the dressing.

In a large bowl, whisk the ranch dressing mix, sour cream, mayo, milk, vinegar, sugar, and dill until combined. Place in the refrigerator until the potatoes are cool.

Once the potatoes are cool, chop them and place them in a large bowl. Pour over a little more than half of the dressing and all of the scallions and bacon. Stir the potatoes until coated in the dressing. Add additional dressing until you reach your desired consistency (you might have a little dressing left over). Taste and season with salt and pepper. Serve immediately or refrigerate until ready to serve.