You do need to remove the washer bottle if you want the ballast completely hidden, it's not difficult to remove the washer bottle but if i was you i'd do it when the bottle is empty. IIRC there is just 2 bolts that hole it in and then you can wiggle it out. The motor is push fit in the bottle so all you have to do is pull it out, i did this with a full washer bottle which is why i recommend doing it with an empty bottle