Zero TDS RO/DI with Copper at 3.61 according to ATI ICP

[ScottB]

I've run a dozen or so ICP over the years and never recall seeing Copper in any of them. This is my first ATI test, and my RO/DI came back with copper at 3.61. The reference level for this is 0.0, but the report did not "Flag" it as out of range. My tank water came back with 1.95.

I gather from other RHF posts that anything under 10 is nothing to worry about. Can I get a confirmation on that?

I run a 7 stage with 2 carbon and cation, anion, and mixed as my final. I show 0 TDS, but where could it be getting through? What should I be more aggressive about replacing even before I touch >0 TDS? Or do I just need to chill out and have a few beers?

 

[blaxsun]

ATI test... probably explains it (I'm inclined to chill and have a beer).

 

[taricha]

This is my first ATI test, and my RO/DI came back with copper at 3.61. The reference level for this is 0.0, but the report did not "Flag" it as out of range. My tank water came back with 1.95.

I gather from other RHF posts that anything under 10 is nothing to worry about. Can I get a confirmation on that?

3.6ppb is likely not far enough above zero to have confidence in the measurement.
No out of range "Flag" is a helpful way of low-key telling you it's not enough uncertainties/ limits of detection above a concerning range.