Will washing baby powder down the drain cause drainage problems down the line?
How much baby powder are you putting down the drain? It doesn't dissolve, but I can't feature that you could put enough down a drain to cause problems. However, I knew of a fellow who eventually plugged his toilet because he tossed his daily piece of dental floss into the bowl, and over the years, it all balled up and plugged the toilet.
My husband created the "Dental Floss Monster" by flushing his floss daily for about 5 years. We couldn't figure out why his toilet was backing up, while mine (separate baths) where I flushed tampons never did. When he snaked the toilet, it looked like an old unraveled hemp rope - grossest thing ever. And of course, I'm saying, "You flush dental floss?" (He quit, of course.)