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.

"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

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" 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?