hi all,this is a wfp question,i have been running my system for the last 7 months, and have noticed that my tds reading is starting to go up, it,s only 1or 2 points so i,m not to worried yet,but i was wondering what you change first,,,,is it the resin, or filters if so which one,,,thanks for any help,,and merry christmass and happy new year to you all...kev