Back December 2011 I had a New Water Softener & Reverse Osmosis Filtering system Installed... Just recently I had the 3 main large filters on the RO changed for the second time.. The Business that I had purchased the systems from has changed hands so the questions are answered differently... lol... My 1st Question out there is, Are the filters somewhat Universal could I not purchase the filters elsewhere and same for the Special Tool for loosening the canister holding the filters? My 2nd question, How often should the 3 remaining smaller filters that sit horizontally be replaced.. Can they be safely replaced as it seems to be a bit more involved? ( the systems were purchased from SimpleH20 , Kitchener,ON.)