My DI turns brown after my second 30 gallon water change but still maintains 3 TDS or under on the output for about 3 months. I personally wait until it reaches 5 TDS before changing it.
After turning brown what is your TDS reading?
No my waste is right after the membrane before the DIIs it possible that you have the waste line connected to the DI chamber?
High co2 will kill resin life. If you have well water then thats prob the problem as that was mine. Easy fix is to run the water out of the membrane to a container with a airstone then pump it back into your di resin chamber. If you need more info just send.me a PM
Goodluck
Greg
What is the TDS reading of just the RO water, not the RO/DI water? That is to say the water after the membrane, but before the DI?