I seldom have a clogged drain, not any at all since the kids grew up and out, and I use the scrub a lot. I'm on a septic system and it's checked once a year and so far we have gotten a good check up.
I use white or brown sugar and extra virgin coconut oil (love the smell). 1 cup sugar to 1/2 cup oil. That's all I use. Here is website that has many basic recipes with variations:
http://wellnessmama.com/3628/sugar-scrub-recipe/