RO/DI help

[Dustin1300]

I said exactly what I intended. DI should not be before RO and in that configuration it was between the sediment and carbon filters before the RO membrane which will not work. It has a little inefficient horizontal DI after the RO also but horizontal DI short circuits or channels and is not efficient so may never get the TDS to 0.
The keys to a good reef quality RO/DI are an efficient high rejection rate RO membrane, the correct DI resin for the application and lots of contact time to do its job. This is accomplished with a properly plumbed and packed vertical DI with bottom up flow so all water and resin come into contact with each other unlike horizontals.

Understood, look back at post. You said there should not be a Di vertical.

 

[AZDesertRat]

Correct. There should not be a vertical DI with that system. The three vertical canisters are ALL pre RO membrane so none should contain a DI cartridge.
IF the user wants to install a vertical DI then they must replumb one vertical housing so it falls after the RO membrane.