Pump Operations
Churn Pressure
Churn pressure is the pressure a pump produces when it is running against closed discharges, moving no water. It is the top of the pump curve — maximum pressure at zero flow.
With nothing open, the pump spins water in place and shows its highest possible pressure for that engine speed. As lines open and flow rises, the available pressure falls away from churn down the pump curve.
Sitting at churn is also where a pump heats up, since none of the energy is leaving as flow. That is the condition recirculation is meant to relieve.