Flows.scala

val src = Source.actorRef[ByteString](1000, OverflowStrategy.dropHead)

FlowGraph.closed(src) { implicit builder =>
      byteStringSource =>
        import FlowGraph.Implicits._
        
        // for junctions / fan-in / fan-out shapes we need to builder.add explicitly
        val broadcaster = builder.add(Broadcast[String](2))

        // for Flows builder.add is implicit, if I'm not mistaking
        byteStringSource.outlet ~> Flow[ByteString].map(_.utf8String) ~> broadcaster.in
                                                                         broadcaster.out(0) ~> Sink.ignore
                                                                         broadcaster.out(1) ~> Sink.ignore
    }.run()