DI Resin - 7 stage - change all at same time?

[11f150]

A little before Christmas I upgraded my RODI from a 4 stage to a 7 stage BRS unit. I'm new to a 7 stage unit. The 3 DI resin canisters reading left to right go cation - anion - mixed. The anion canister is half depleted with the other 2 canisters still very dark. I came across a concerning post on FB that someone running the same setup didn't know their mixed canister was depleted and almost crashed their tank. I was under the impression that my anion canister or any of them would only need refilled once they are depleted (color changes). Is this the case or do they all need refilled/replaced once the anion is depleted?

 

[MERKEY]

Some replace all 3 at the same time.

I Just replace them when they change color.

To make sure you are getting 0tds use a 3 line tds meter

 

[rtparty]

Just replace the anion. I replace the anion 3-4x before I need to change the cation.

Anyone almost crashing their tank because the mixed depleted, isn't watching their system or TDS very closely.

 

[11f150]

Thanks for the replies. That is what I was thinking but wanted to make sure.