Mr. Kumar is correct in all the above, problem is now you have to determine which one it is and how to correct it. Most of the time I have found it to be a Engineering design issue by Turbulence, improper positioning of elbow, strainer etc.. but the best way I have found to determine this is by using an Ultrasonic leak detector head-set. Using this can help you determine the location of the cavitation then guide you to what you should be looking for i.e. bad pump seals, cavitation in the housing . Best wishes and let us know what you find. Engineers can also design a flow positioner that can be placed inside the pipe to correct flow conditions that have been measured and verified.
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