you need to periodally take out the seat post (more so if it's carbon post) out of your carbon seat tube and wipe the post and inside of seat tube and turn it upside down and pour the water out of the frame. More so if you ride in wet conditions but even if you dont. Else your seatpost will fuse to the seat tube after a while.

I perform this procedure every 4 weeks.

Naturally, mark the seat post height *first* so you wont lose the exact saddle height.