Cleaning Water Tank / System on 1999 Symbol

Hello to all. First I must say that I hope members are keeping well and perhaps using all this spare time to work on their vans ! I want to clean the water tank and pipes on my Symbol. I understand that Puriclean is a good product for flushing the system and that Puri Sol can be added to keep the water fresh whenever the tank is filled. The instructions from Puriclean though also mention changing the water filter ? Does anyone have experience of this ? To be honest I don't even know where the filter is and where I would get a replacement. As always, your help would be very much appreciated.
Keep safe
Rob

You don't need to do it twice!!  

Suggest you do a search. This question comes up quite regularly. I'm sure you'll find numerous responses.