filter normally situated behind or in a kitchen cupboard possibily under sink as thats where water feed will come from .. easy changed
ebay you best bet to purchase one ..there quite few listed but this is a genuine one ..
Item number: 280624967372
hope this helps
you can also get some good info on samsung via this guys youtube channel ... best to copy paste this into your web browser ..
http://www.youtube.com/user/SamsungFridgeFreezer?feature=mhum
very helpfull - fully qualified samsung engineer who specialises in samsung products that are out of warranty ..
maybe best checking this item out as well re water filter , reason being if you are changing your filter if you water isnt working it may mean you may have a fault ... check out this listing on ebay there is a video in listing which list certain symptoms that can develope with the rs21 model ...
lItem number: 280596204942
hope this helps ...
calum, February 2011
