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RO/DI.. stubborn high PH?

449 Views 2 Replies 2 Participants Last post by  zodduska
So I recently invested in a spectrapure RO/DI unit to finally have control over my water parameters. For some reason the PH doesn't behave the way I believe it should.

TDS of the DI is 0, PH 8.2. The source is very hard well water that passes through a water softener, before the softener its GH > 25, KH > 20, TDS 650, PH > 8.

I've remineralized using Salty Shrimp GH+KH to
GH 7,
KH 5,
TDS 220.
In my tank with Aquasoil, with a lime green drop checker the PH measures 7.2. It would rise to above 8 again if left sitting out overnight. There's also mopani driftwood in this tank. My Small non co2 tank is PH 8.2 with slightly softer water param, GH 5 KH 3. No aquasoil in this one. Nothing in either tank is causing KH increase.

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That pH sounds too high for that level of KH. There is something in the water doing this.

Here are a few links to info about RO and the pH and KH of the water before and after treatment. (not aquarium related sites)

They indicate the pH should be lower, not higher after treatment. But they also show that even a very small amount of something added to the water can make a big difference in the pH of the water.
Thank you Diana. I just checked the calibration of my cheap PH pen, it was way off and I should have done it before posting this. Sorry for wasting your time.

As a side note, I have calibration liquid from Atlas for PH 7 and 10, when I calibrate for 7 the PH 10 solution reads PH 9.5. Not sure if that's how it's supposed to work or maybe it's time to replace the pen.
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