We did an APU run to test the PFCU we’d just changed on an F3 during a Primary servivcing in a HAS (no ground cart available). What we failed to do was check the rest of the system… the entire contents of the jet’s hyd system emptied through a vertically-pointing pipe and soaked the HAS roof. Thing is, what goes up, generally has to come back down….. 5 wet riggers and a flooded HAS….. We needed more than a rag to prevent that elbow drain….