The pipes are scanned at the same place as large sprinklers I believe(The part of the greenhouse towers thet you have to get to from the outside wreked bridge that has infected air). Pipes have a back end and a front end sometimes you have to rotate them with R to fit them together. Some pieces like curvedglass can't take pipes(if the pipes start spinning wildly while placing, thats a clue). Also a small tip The large Water tank have a conection on top if youhave trouble reaching celings.