As I reported in 38821, the valved out section of the corner station plumbing showed a curious pressure trend.  And this behavior continues.

The attached plots shows 50 hours where you see the output pressure of pump station 1, the supply pressure on the main trunk line (mainsupply) and the two sensors on the distribution manifold beneath BSC2 SUP & RET.

At the start of the plot just before the start-up pressure spikes, the valving to the LVEA was changed to put the Pump Station Array into recirculation mode. This is when the BSC2 pressure sensors started their trend up.  On Wednesday towards the end of the day, the pump stations were stopped but the BSC2 sensors continued their trend.  Yesterday, the pump stations were restarted to continue the recirculation.  One can see that the behavior of the BSC2 sensors was the same as the night before when there was no pressure at the pump stations.  The PSs are again shut off now and the BSC2 sensors continue  unabated.  I predict this cycling will continue until the valving is changed back to the operations configuration.

FYI, all the actuators in the LVEA are valved out (or bypassed) so the entire LVEA plumbing is one big U, complicated at the bottom end with lots of branches and loops up to the BSC actuator bypass valves.  While there are a few top point air bleed out ports, I believe these are all closed and not leaking.

We guess it has to do with siphoning around in the closed system but 20+ psi seems too large to be explained by the height of some of the plumbing above the pressure sensors at BSC2.

Now done with the local recirculation and will start filter changing next week.