So it sounds like the head of pressure to the pump inlets was due to gravity.
Since both the internal tank and the outside tank are much lower then the higher rows of Prominents, just gravity alone can not feed the Prominents.
If we had just gravity, those higher Prominents would have had a negative inlet pressure
The Prominents can maybe overcome this negative pressure by the sucking action as they increase their internal volume during the inlet stroke but I find this an unlikely scenario.
People keep bringing up this idea that the internal reservoir for the E-Cat plant is sealed and has a head of pressure on it. But in this case I don't understand how the external reservoir sitting outside the E-Cat plant, feeds the internal reservoir by gravity as described by Penon and Barry West.
In case the internal tanks have a pressure on it, then that pressure can feed the Prominents with a positive inlet pressure while at the same time due to the hight difference between the external tank and the external tank can feed the internal one. The water pressure is possibly provided by the additional pump on the JM side which AR describes in his notes about the Smith report.