How much CO2 is in your tap water?

[Bill Stock]

My tap water has always had a PH around 7.5. But lately my tanks have been
running over 8, where they used to be around 7.6 - 7.8 in the past. So I
tested the KH (5) and PH (7.0) of my tap water, which would seem to indicate
15 ppm of CO2. I'm a little surprised to find it this high during the summer
(warmer water). I'm letting a batch of tap water sit, so I can test the PH
after the CO2 escapes.

I don't know what the KH was in the past, the city water documents no longer
list KH or DH.

[djay]

"Bill Stock" > wrote in message
...
> My tap water has always had a PH around 7.5. But lately my tanks have been
> running over 8, where they used to be around 7.6 - 7.8 in the past. So I
> tested the KH (5) and PH (7.0) of my tap water, which would seem to
> indicate 15 ppm of CO2. I'm a little surprised to find it this high during
> the summer (warmer water). I'm letting a batch of tap water sit, so I can
> test the PH after the CO2 escapes.
>
> I don't know what the KH was in the past, the city water documents no
> longer list KH or DH.
>
>
>
Check the phosphate level of your tap. Phosphates can bugger up a pH
reading.

Djay

[Rocco Moretti]

djay wrote:
> "Bill Stock" > wrote in message
> ...
>
>>My tap water has always had a PH around 7.5. But lately my tanks have been
>>running over 8, where they used to be around 7.6 - 7.8 in the past. So I
>>tested the KH (5) and PH (7.0) of my tap water, which would seem to
>>indicate 15 ppm of CO2. I'm a little surprised to find it this high during
>>the summer (warmer water).
>
> Check the phosphate level of your tap. Phosphates can bugger up a pH
> reading.
>

I was under the impression that phosphates mess up your KH reading, not
the pH. (As the KH test isn't a test for carbonate itself, but rather a
test for buffering, and phosphates act as buffers.)

Either way, if there is phosphate in your water, the calculated CO2
value would be off.

[Bill Stock]

"Bill Stock" > wrote in message
...
> My tap water has always had a PH around 7.5. But lately my tanks have been
> running over 8, where they used to be around 7.6 - 7.8 in the past. So I
> tested the KH (5) and PH (7.0) of my tap water, which would seem to
> indicate 15 ppm of CO2. I'm a little surprised to find it this high during
> the summer (warmer water). I'm letting a batch of tap water sit, so I can
> test the PH after the CO2 escapes.
>
> I don't know what the KH was in the past, the city water documents no
> longer list KH or DH.
>
>

Thanks for the information. Tap water tests 0 for Phosphate, but I was
adding it to the tank for the floating plants. So that might explain the PH
readings in the tank.

I tested the PH of the tap water that I let sit for 24 hours and it's still
about 7. So now I'm really confused. Can the KH change with the outgassing
of CO2?