You lucky so and so a tds of 47
Yes there are filters, for that system I would look at the RO-man site!
I take it your using resin after the RO!
If you want to lengthen the life of the ro filter use a softener before the ro!
My system is like this:
Tap - Debris Filter - softener- RO (has a carbon filter built in)- DI resin - storage tank
As long as the readings tds is 000 at the end of the prodess no worries! :
However as stated the way you set up your system will determine the length of your filters