If your pump is cavitating and significant bubbles are seen at the pool return ports, your pool pump HP may be too high for your pool system. Your pump may be trying to pull too much water through your suction piping than the system can handle. For example your pump is set up for 2" piping and your system has only 1 1/2" piping. You might need a smaller pump. One way to accomplish this reduction without having to buy a new motor, is to downsize you pump's impeller. This guide shows you how to reduce the HP of a pump by reducing the size of its impeller. Although this guide is based on replacing a Hayward motor impeller, many of the step are applicable to other makes of motors.