Is the pipe diameter changing at the nozzle or the node in the fire sprinkler system?

the branch pipe is reduced after each nozzle tee; The nozzle diameter is changed at the nozzle interface. You can check the specification or refer to the last nozzle in the figure. As shown in the figure, the diameter of the last nozzle is DN25, and the nozzle is DN15 (which is generally marked in the design drawings). If the nozzle diameter change is at the node (tee), the pipe diameter should not be marked DN25, but DN15, so the diameter change should be at the nozzle.