I got an Ionic system, and do buy refils from them but to be honest I havent bought any from them for just over two years now as I do maintain the system every day and although they state changing some every 300,000 l I still havent and have gone way over that and my water is still coming out at 0ppm, even the DI filter has still got the blue coloured resin in it and still has probably about 5/6 months of life left before I have to replace it, and I will only go by my tds as to when I need to change them