The Impeller on the Aquabot Rapids 4WD Robotic Pool Cleaner is the fan blade on the inside of the unit that creates the vacuum action to clear debris from your pool. Due to the wear and tear on a cleaner, heavy debris or possibly user error, the impeller on an Aquabot Rapids 4WD Robotic Pool Cleaner can become damaged. This is a simple and easy part to replace. Simply follow the step-by-step instructions in this guide. Note: This guide can also be used for the Aquabot Breeze 4WD Robotic Pool Cleaner.