I am hoping to order my RO/DI system this week but the seller has me confused. They've mention that I can add a RO Bypass, which to my knowledge is actually a DI bypass. If I am not mistaken, this bypass is used to bypass the DI section as water from the DI is not good for drinking. What exactly does the Di section of the system do and is there any other reason to bypass it other than for drinking? My system will be installed in a spare bathroom so we wont be drinking the water from it. We will be using it for both the saltwater and softwater/freshwater tanks.

Any info appreciated.