<a href=showthread.php?s=&postid=14029319#post14029319 target=_blank>Originally posted</a> by Tswifty8
I also would replace them all (except the RO membrane). I used to use The Filter Guys, but finally after having it beat into my head that "spectrapure was the best" I decided to try their DI Resin out. It's already lasted over twice as long as my previous DI's. I'll only be purchasing their filters from now on.
There's also a disinfection procedure you'll probably want to perform on the unit before you install the filters. I have it here somewhere. I'll have to see if I can dig it up for you.
The rule of thumb I've seen... is 6 months like clockwork for replacing all your pre-filters, and the DI every time you start to see TDS in the output.