Re: NANFA-L-- hardness and pH

Jerry Baker (
Fri, 26 Aug 2005 07:20:28 -0700

Hardness only serves to buffer pH changes. It doesn't necessarily change
the pH directly. Water utilities usually increase the pH of tap water
significantly to keep it alkaline. The reason is to make sure there are
no pockets of acidic pH in the system. Acidic water picks up lead from
old pipes, and corrodes older galvanized pipe.

The most common reason for a high pH with low hardness is low dissolved
CO2. With a hardness of 2 DKH, and a CO2 of 0.5ppm, you would expect the
pH to be around 8.1. That's normal. Just increasing the CO2
concentration to 6ppm will make your pH 7.0. I believe just stocking a
tank with fish will be more than enough to accomplish 6ppm CO2.

Laura Burbage wrote:
> I've got a chemistry question. The water here in
> Athens is very soft, less than 2 GH and KH. But it is
> persistently alkaline, around pH 8 or more. Why on
> earth is this? What can I do when I am working with
> tap water to raise the hardness without raising the
> pH? How can I lower the pH?
> Laura
> North Oconee River
> Georgia
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