As you can see you don’t get a ‘hot plug’ in the heat exchanger section of the system because with the addition of the thermosiphon the water is circulating to the ‘cool’ group and back again, so no flushing is required before pulling a shot. This assumes the thermosiphon i system in your machine has been designed by someone who knows what they are doing, and that your machine hasn’t been abused – i.e. solid with limescale