"CURTIS HOOD" wrote in message
...

my ro-di puts out about 12 tds (total desolved solids ) distiled water =
35 tds and my tap =327 tds . however tds does not show copper ...


Anything above 5 for use in Reef tank, I would say that not too good. But at
the same time, if this water is for human consumption, then it good.
You might look into a test kit for copper reading.

If you do have a working RODI, it should not have anything higher than 1ppm.
Before DI and RO only should see like about 3 to maybe 10.

Anything above 6ppm, this maybe your RO unit maybe depleting it usefullness
for reef use. But again, you still can use it as human consumption until
over 20ppm. Bottling water that I check like ArrowHead / Alhambra .... from
my TDS reading show about 15ppm avg.

If it hit above 5 or 7ppm, you may need to check if your sediment / carbon
block is depleting. Otherwise, your membrane may need to change.

You may need to check what the result of each stage.

CapFusion,...