I would probably just use WaterGEMS to compute the HGL at J-1 when PMP-2 is on and PMP-1 is off...
But you should also find that the HGL at J-3 is the same as the HGL at J-1. That's because there is no flow from J-1 to J-3 (so no headloss)...but they are still connected hydraulically so J-1 'sees' the HGL from J-3.