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jacob.morgan78
08/23/2016, 11:34 AM
Would the presence of copper show up on a tds meter when checking RODI?

Would DI resin take copper out of water?

Thanks!

hkgar
08/24/2016, 05:11 PM
Mu understanding is a TDS reading of more than 0 means something is there. It could be copper. Not sure where but somewhere between the pre filters, RO membrane and the DI resin an reading of 0 would mean the copper has been removed.

disc1
08/24/2016, 05:29 PM
Remember that most of our TDS meters read in ppm. It only takes 50ppb of copper to nuke a tank. 50ppb (that's 0.05ppm) would read 000 on most TDS meters.

Yes, DI resin will pull copper out. It will pull it really well. And since there is so much more other stuff in your tap water, if you see 0 you know the DI is working so you can rest assured it's getting all the copper. Once it starts to creep up at all then all bets are off. Copper isn't the first thing that will break through, but it is pretty high on the list.

outssider
08/25/2016, 05:36 PM
Copper isn't the first thing that will break through, but it is pretty high on the list.

What would be some of the first things to break through ???

disc1
08/25/2016, 06:22 PM
What would be some of the first things to break through ???

Our resins are strong anion and strong cation exchangers. So they have the least affinity for the larger "softer" ions with lower charge density. So on the cation side you're talking about things like ammonium. On the anion side it's things like phosphate or silicate. And it's not just that those things pass through depleted resin, once the resin is depleted, the smaller "harder" ions with higher charge density like sodium, calcium, or magnesium will actually displace those softer ions from the resin and you can end up with water that is worse than what you started with. Think of it as the sodium in the tap water "washing out" the ammonium that was already trapped there or the chloride in the tap water "washing out" the phosphate that was previously trapped there.