Use a filter cleaner to clean your cartridges.  A filter cleaner will remove the oils that have collected on your cartridge.  The new spray on cleaners work very well and quick. 

Note:  Do not use muriatic acid to clean your cartridges before using a filter cleaner/ degreasor or you will burn the oil into the cartridge, reducing is life and also it cycle between cleaning. If you noticed you get less life between cleanings either you used muriactic acid to clean or your did not use a filter cleaner.  VERY IMPORTANT!!!

Also remember to let the grids or cartridges dry thoroly before reinstalling.  Installing a wet cartridge will reduce is filter cycle and you will have to clean sooner than you want.   THIS IS CRITICAL!!!

Always have a spare cartridge on hand!!!