When/What filter to change?


I have been using my 5-stage RODI unit for about 6 months now. I recently purchased a TDS meter and calibration solution. After calibrating here are the test results.

Tap water- 761 ppm
After RO- 42 ppm
After DI- 19 ppm

I was pretty surprised that I got such high readings, I was hoping for 0 after DI. Is it time to change the DI filter or all of them?

Is the DI 19 ppm because the tap water is so high??
Wow that is high incoming TDS!!!!!
Without knowing where you started, it is hard to tell if it is time to change them. I replace mine about once a year, but my tap water is at 120 ppm so they will last longer than yours would.
From what I have been reading it sounds like with tap water that high a 5 stage rodi will not be able to get it to 0. What do you think I need to add? Another prefilter, or another DI to my exisiting unit?

This makes me want to add a whole house filter for our drinking water...
I would call and talk to the guys at The Filter Guys
See what they suggest.

as far as when to change, i always get zero tds out of the DI but usually by the time the resin changes color things are slowing down and getting clogged so that's when i change the DI and filters. The membranes i change once a year or so.