RO PH

[swatchguy]

I'm trying to figure out the tank chemistry involved with my BC29. When I test my
RO water for PH before mixing it with salt it's below 6.2. That is too acid. I have an ATO which does about 1 g/day. My main tank PH is 8.4, even with the addition of PH 6.2 RO water. alk is above 8 and CA is 400.
I'm wondering if "kalking" will do me any good. I tried it for awhile but it didn't seem to matter.
Mixing my own sea water must buffer my RO water so that the resultant tank water is ok. I've read Randy's chem but I'm still in the dark. Can anyone net this tank chemistry out for me. Thanks, Swatchguy (Steve)

 

[Gomer]

RO water could easily be 6.2 and that may not be an issue. RO water technically should have zero buffering capacity. Since the water is exposed to air, CO2 can dissolve into the water to form carbonic acid causing your 6.2 reading.

 

[Mr. Ugly]

Yep, pH of RO water isn't a useful measurement. Without buffering, tiny changes in dissolved CO2 can cause big swings in pH.