Help with water changes, ATO and patience :)

[lastlight]

If you watch your Tds out if the ro membrane you'll notice on startup there is a large spike before it hits it's stride. This is Tds creep and I use a valve to divert ro water straight down the drain until it subsides then allow it into the di resin. Not doing this and also allowing the unit to turn off and on itself without bleeding this Tds off will exhaust your resin much faster.

[Reef Pilot]

I have a before/after TDS monitor on my RODI system. I have only ever seen 1 or 2 tds (mostly 1) after the RO membrane, and always 0 after the DI filter. My incoming tap water is around 40 - 70. I also have 2 pressure tanks (3.2 g each) after the RO membrane (and before the DI), so that provides some buffering of flow from the membrane. And I have an RO only feed to a faucet on my kitchen sink, so I don't waste DI resin when filling water bottles or whatever.