I think for 20-$40 you can pick up a TDS (Total Disolved Solids)
monitor. This will tell you exacly how well your RO/DI filter is
working. When the readings start going up... time to replace the
media... As long as you replace the other 3 cartriges (which are
cheap. all 3 for like $20) you shouldn't have to replace expensive one
very often....
TheRock wrote:
Something I've never pondered much, BUT
it's time for me to purchase some more RO/DI filters and media.

Well just for kicks I tested the tap water (public water)

0 Phosphates
0 Nitrates
0 Nitrites
0 KH
6.2 pH
0 GH Very Soft

It's pretty good water.
OK except for that Chlorine stuff.

What else should I be concerned about with tap water
that RO/DI removes ? Silica, Iron etc ???

I would be nice if I didn't have to spend anymore cash on filters...

Thanks,
Chris