This HEPA cartridge filter is designed to protect your Panther and avoid fine dusty particles from entering into your Panther’s head and potentially causing damage to the motor. The use of this “high-efficiency particulate air” filter should be kept for dry use, typically when we haven’t had rain and the gutters are dry and dusty. You can remove this filter when the gutters are wet as you have your wet use blue filter to protect the float valve. To really optimise the lifespan of your HEPA filter, clean the HEPA daily (at the end of your work day). You can do this by using a brush or a vacuum. When the filter has a high level of dirt content you can run the HEPA under running water at room temperature with a soft flow. A delicate detergent can be used in very small quantities. Please do NOT use a pressure washer to clean your HEPA as you will risk damaging the filter. If you do wash your HEPA filter, please ensure it is bone dry before next use.