Color Change DI, help me out here.

[mjsandbe]

I have a question about DI cartridges in RO/DI units. I have a DI cartridge that is "color change". My question is what color should it change to. New is mostly black with some white on the bottom. My old one that is a year old was a solid rust brown when I pulled it out. Should I be expecting the black to retreat and the white to expand or what? It is a five stage unit with a sediment filter, 5 micron carbon, 1 micron carbon, 100 GPD RO membrane, and then DI.

[dwall174]

They usually go from black or green to a light brown or orange/rust color. You should be able to see the color changing from the bottom to the top.

[mjsandbe]

Thanks, it has such an obvious name but the details escaped me.