Knowing the head and the impeller size, you can determine the flow of the pump. Now that we have the flow and head of the pump, let's see how close we are to the design point. Most often, the head will be less than what we expected, and the flow will be more. There are many reasons, but it does no good to blame anyone. Let's just fix the problem.
Solutions Trimming the impeller is one of best solutions.
Before we can trim the impeller, we need to determine where the pump is operating. Along with that is our actual system curve. Remember that we are concerned with the actual system curve. This shows us how our system operates, not how it was designed. Operational and design points are often completely different.