I would say that they are highly recommended...better than having to take the whole thing apart when you find out that you still have air in your setup cause of some air pockets that didn't get out when you submerged it. To add it in, just get a T barb (I got mine from Home Depot) and stick it in the system, with the T being at the highest point of that section of tubing. I put mine right after the pump, but right before it would probably be just as good. Or anywhere else, really, but if you split your tubing off (say, for Northbridge or video cooling) then you'd want it before (right after the pump) or after (just before the pump) the splits.