how to get an accurate CO2 level

[tazcrash69]

While I'm in the process of aquiring the rest of components I need to finish setting up, I tested my tap water, and found out the following:
PH: 7.3
KH: 8
CO2 accoring to the charts, and calculator: 12.

Now this tells me that I have some other kind of buffer in there which is giving me a false CO2 level.

Is there anything I can do to get a more accurate reading?

 

[TankGirl]

Did you wait a day to allow any CO2 in your tap water system to outgas before you tested? Your pH may be hgher than that.

 

[workfortheman]

Agreed with TG, especially with that high KH. Let it sit for a day then keep us posted! Otherwise, you could question the accuracy of the test kit.?.?.?

 

[Xzap]

Isn't a kh of 8 high from a tap ? I'm on city water, mine's 1dkh.

Dave

 

[workfortheman]

Yea, mine's 4 and I thought that was high!

 

[TankGirl]

Mine's 5-6, but my pH is about 7.6. There are plenty of places with a high KH, GH and pH out of the tap, and some even with high GH and KH but a neutral or acidic pH, but that is not typical. If you have KH of 8 you assume the pH is going to be higher than 7.3, but it is not unheard of.

 

[tazcrash69]

I just moved from NYC to a NJ suburb, and the water is very hard here. White crust on quiet a bit of things. I also hate the taste. I'll let it sit overnight, and try again. Thanks for the input.

 

[wierdkid]

thats nothing, where i used to live Kh and GH were both over 15(town water not well). it all depends on local bedrock, the town was right at the base of a huge limestone escarpment (KH is caused by dissolved limestone)

 

[rich311k]

Just curious. I thought the kh ph Co2 level test wasn't accurate unless you are actually injecting CO2.

 

[malkore]

Rich,

No, Kh and pH for CO2 is always accurate enough unless there's another strong buffer present.

That's the reason tazcrash is concerned...their pH is lower than it should be for a dKh of 8.

Let your water sit overnight, with an airstone running in it if you have one. This outgasses any CO2 in the water and would bring the pH back up.

My tap pH is 7.8 and dKh of 8~9. city water, but it comes from a huge underground aquafir made up of limestone and calcium rock.

 

[rich311k]

Thanks Malkore. I thought I read that somewhere, Thanks for setting me straight.

 

[tazcrash69]

OK, I retested after letting some water outgass, and that seems to be the culprit.
My PH went up to 7.6 & my KH was still at 8 degrees, which claculates out to CO2 at 6ppm.

So does this mean that I have other buffers in the water?

 

[TankGirl]

I'd be suspicious of my arch nemesis - phosphate. Check that from your tap and see what you get, and compare it to your tank.

 

[tazcrash69]

My tank is not set-up yet, I was just getting a base line. The phosphate test kit is on order.

Thanks all

 

[malkore]

and even if you do have too much phosphate, acting as a buffer, its not much, as you're only showing about 2ppm over what normal non-injected levels would be at, so you can just subtract 2-3ppm from the final value.

However, it also might be worth having the LFS test the pH of your rested water...in case the test kit is being a little more inaccurate.

 

[tazcrash69]

Thanks for the advise Malkore. I'm still looking for a really good LFS in my new neighborhood, and this might actually be the litmus test