What you might want is a factory performance test, which will give you a certified curve. You'll pay extra for it, of course.
The manufacturer can't guarantee how a pump will perform in your installation, but they can guarantee its performance on the test stand at the factory.
There are standard test codes which set out guaranteed performance tolerances - in my opinion the ISO tes code is the best but depends on where you are in the world as to which code is used.
It depends on your goals and how critical the pump performance is> However in general
The Hydraulic Institute test code class A is the most stringent.
ISO 9906 is widely used and has 2 classes of acceptance. In my opinion class 1 is ok for most general purpose pumps. Class 2 is so lenient as to be useless.
There are other codes out there such as DIN 1944, API 610, ISO 3555 and ISO 2548, but these are less widely used.
