You must turn the heater control for the heater back to 55................have the same exact size as the one that you have, they also permanent ones that you can hose out on both sides. Take out the old one, use your vacum cleaner and clean in & around that area with your brush attachment using a flashlight or drop light.....last clean off the metal or cement bottom. Put the new filter in place and make sure it is secure. Reset your heater control to it's original setting.