[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.

Sigh..

 

[Diana]

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)
http://www.freedrinkingwater.com/water-education2/ro-ph.htm
http://www.puretap.com/ph.htm

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.

 

[zodduska]

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.