Water filter system

My house Diamond filter giving me problem again! the output is not as fast as last time even after the back wash done on it!! And the inside..haih, eventhough we been washing regulary, the system inside was yellow in colour! I know it is not the filter problem and the problem lies in our water quality but then again, if the system inside is yellow in colour mean we will be drinking it as well..How can i clean the system when the dirt did not go away? Maybe I should give home hepa filter system a try when I change my Diamond filter system next month!