Manaul for 550/850xp says that water can get into PTV system, and that the proper way to service is to take out the drain plug, let water drain, reinstall plug then rev motor up - repeat if necessary - so where is the drain plug??

 

Not sure about the new xps but the CVT plug is below the belt housing cover,but I quess you already look there. I think its red in color.

 

Small red plug on bottom of CVT housing. Port side of vehicle. It screws out. I just keep mine hand-tight, doesn't leak and that way you don't need to get any tools out when you get back to dry land.