The location of the pool pump impeller is shown in this cut-away of a pump. The spinning action of the impeller when driven by the pump motor generates the water pressure in your pool system. Sometimes debris will get into the pump and will crack the impeller. In other cases the threads that hold the impeller to the motor shaft become worn causing the impeller to wobble and rub against the diffuser. This guide explains how to replace a bad pool pump impeller.
For a quick introduction, this picture shows the operation of the impeller. Water enters the center of the impeller. As the impeller is spun by the motor, a series of blades, like a fan, pushes the water to the outside edges of the impeller where it exits through slots to be collected by the diffuser. For an expanded explanation of how a pump operates click How A Pool Pump Works.
Place a 7/16" wrench on the flat end of the motor shaft to secure the shaft from rotating. Note: Securing the motor shaft on other non-Hayward type pumps varies. Some pumps provide a slot on the end of the shaft to secure with a screwdriver. This slot is often accessable by simply taking off the end cap of the motor.
With the impeller off you will see the motor shaft seal. One half on the impeller and the other half in the seal plate on the shaft. If you have not replaced the motor shaft seal and the pump is several years old, this may be a good time to replace this seal. For instructions on replacing this seal click How To Replace a Motor Shaft Seal. If you decide not to replace this seal, continue on to the next step.
Grab the seal on the impeller and twist it off. Make a note of how the seal is positioned on the impeller so you know how to place the new seal. It is possible to place this seal upside down. Note: You may have to also have to remove the metal collar if the new shaft seal also has one. Several people have written in saying that the new seal won't fit because they were trying to place the new collar on top of the old one. DO NOT touch the bearing (top) surface of the seal. It can corrode the surface.
Replace the four bolts evenly. If bolts were numbered 1 though 4, replace bolts in this sequence - 1, 3, 2, 4 - to ensure that the motor is set properly inside the housing. Loosely tighten bolts in this sequence, then go back and tighten them down again in this sequence. If pump has 6 bolts, replace bolts in this sequence - 1, 3, 5, 2, 4, 6.