Err, there isn’t! There are previous threads on this including one with photos of the whole system. When I say system I mean badly designed collection of tubes vaguely connected together in places, and apparently not even that it turned out on mine!
Best you can do is regularly hoick any clag, leaves, moss or seeds out of the holes in the rubber at the bottom corners of the rear window, and regularly vacuum out the rear parcel shelf so that the dry ones that waft in don’t pile up round the internal gratings behind the seats.
This should be the link that gives you the best info…