The lift pump is not a constant pump. The specification you mention is with the output of the lift pump open of course so the pump would be constantly working. In use it is designed to work until a certain pressure is developed. Controlled by the regulating spring. Then it just semi idles until the pressure drops and randomly tops it up.

It is pretty early in the morning here and i just got up. I am far from wide awake. I heard the wife say my name. So figured it was time to get up. I now think she was coming back to bed and wanted her side of the bed back. Anyways here I am hours earlier than I normlly get up fully dressed

. Better test and the one I trust more is pressure developed. You cannot have pressure developed with not enough volume available. To create it. Plus on an open flow test you have no indication of the regulating springs Functional pressure intent.

For example you can totally close off the output. The pump will work until the designed spring pressure is reached and then stop working. Just holding that pressure. There also are two check valves in the pump. Open flow test does not indicate the condition of the output check valve.

Dynamic testing is better anyways. When pump is in the system. It may only pump several gallons per hour. If that much. That may be why these pumps last so long in service. They really are not pumping all the time.