This is RO water dispenser. Prepared to filters change. 
With 4 elements filters, Dollton Sediment, Dollton Pre-Carbon, Olsmopure Membrane & Dollton Carbon Block. 
When i open the Step 3 Membrane casing, the membrane filter is very dirty. 
Replaced it done.
Also replace the new tubing, one is inlet water & one is drained water.
Done. 
Discarded the old filters. 