I moved into a new house and have been having issues with copper in the tap water. Levels are at 1.07ppm. Never thought about it affecting the tank because of my RO/DI unit. However something told me to test my tank water and indeed there is copper at .04. I tested my RO/DI water twice and both times it registered .1. Suffice it to say I am running cuprisorb in the tank and I'm throwing out my RO water and the fresh saltwater I was mixing. My question is, what part of the RO/DI is failing to remove all the copper? Is it the membrane, the carbon, or the DI resin? I will replace the carbon and DI regardless and rinse the membrane. The membrane is less than a year old. But which part of the filter is the culprit?