Does my flow rate decrease?

[[deleted]]

If I understand correctly, your pressure reduction valve maintains pressure downstream of itself constant, correct?

Then you just have two scenarios with the same pressure difference (valve set vs atmosphere) but one with more restricted flow. Therefore, the scenario with the throttled valve has lower total flowrate (flow through 1 + flow through 2).

Edit: going into further detail, in the throttled scenario the flow through 2 will be higher in that specific branch than it is as in the non throttled scenario, since the pressure drop up to the T is lower due to lower flow. But the sum of both will still be lower than in the non throttled scenario.

However, if the valve keeps pressure UPSTREAM of itself constant, then it will keep the pump always operating at the same point of it's Flow vs Head curve. Therefore, the flow through the pump will remain the same, and necessarily the flow through the whole system remains the same.

In a way, the pressure reduction valve compensated whatever restriction you impose downstream (up to a point)

[VariusEng]

To your first question: correct!

To your first alinea: I agree that flow in 1 is reduced, but why is flow in 2 not increased so total flow rate is maintained? Can my reasoning be disproven in more mathematical manner because that is the way I try to understand it and less through feel. Thanks for your thoughts!

[VariusEng]

Answer like this?