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Re: probable buffer?


On Tue, 29 May 2001, J Miller wrote:

> My local tap water is sruprisingly pure - not too much of anything
> accoridng to the water report for March (for some reason, they are
> always a few months behind on their website).  I am wondering if there
> might be a hidden buffer - something that isn't normally tested for.
> If not, would the pH drop one its own through aeration (ie, add CO2)?
>
> Here is doday's report:
> Hardness (ppm CaCO3) 167
> pH 7.80
> Alkalinity (mg/L) 112

Alkalinity at 112 mg/l is fairly well-buffered.  That comes out to a
little over 6 degrees alkalinity.  That alkalinity plus a pH of 7.8 gives
you about 3.5 mg/l CO2 from the tap.  If you aerate a sample of the water
then the pH should increase.  Unplanted tanks and planted tanks with only
slow growth but without added CO2 usually have 3-4 mg/l CO2.  You might
not see much difference in the pH of your tap water and the pH in an
aquarium.


Roger Miller