Water utilities are (justifiably) very protective of their infrastructure. Justifiable because of the extreme expense in closing a street, excavating, and repairing anything that happens to their buried infrastructure. I've seen the one in my city reject a stormwater pipe because of a couple small pieces of crusher dust. I can't see them being positive towards the deliberate installation of another biofilm-forming-surface inside their pipes. But YMMV I'm only speaking from experience in my small neck of the woods!