We all face a very common problem of how to measure the performance of an inefficient pump in absence of flow meters particularly in case of cooling water pumps where usually there is no flow meter.

Based on my past experience in energy audit for last several years I found that we know the pump is not upto the mark based on its physical apperance of corrosion, leakages, sound etc. but how to prove it based on data that too when it is delivering the design head when you measure discharge & suction pressures. This is very confusing.

Read the simple method to verify the performance. You only need the performance curve originally supplied by the manufacturer.