Water Chemistry

[timbruun]

So i just got a water conditionner installed. Figured I'd compare the tap to the 2 tanks i have. Only things i have a problem with are out of the tap my pH is about 7.5 and tanks is 8.5, which i'm pretty sure is co2 coming out of the water because it does the same while sitting in a pail for 48 hours. but i bought a kh and gh api test kit and i'm not sure if i'm doing it right. it took 25-28 drops from the kh to turn the water from dark blue to full yellow in tanks and tap. and the gh took 5 drops in tanks and tap. but the gh wasn't really that green, just a pale green. but it was somewhat a pale green after the first drop. does it need to be a dark green? thanks in advance.

 

[timbruun]

bump

 

[raptorrex]

So i just got a water conditionner installed. Figured I'd compare the tap to the 2 tanks i have. Only things i have a problem with are out of the tap my pH is about 7.5 and tanks is 8.5, which i'm pretty sure is co2 coming out of the water because it does the same while sitting in a pail for 48 hours. but i bought a kh and gh api test kit and i'm not sure if i'm doing it right. it took 25-28 drops from the kh to turn the water from dark blue to full yellow in tanks and tap. and the gh took 5 drops in tanks and tap. but the gh wasn't really that green, just a pale green. but it was somewhat a pale green after the first drop. does it need to be a dark green? thanks in advance.

wish i could help, but you give too little information.
we could do with:
PH
KH
GH
but we need readings, not colours!
CO2 will will, lower, PH not up it. i am also, fairly, sure. you need to actively remove CO2. its not good at gassing off.
still cant say anything else till we have FIGURES, instead of colours.

 

[Truck]

CO2 is incredibly unstable when dissolved in water and will gas of very quickly with surface agitation

 

[timbruun]

you're right. co2 will lower it. hence when water comes out of my tap and sits for a while, the co2 gasses off slowly and ph rises. that's the only explanation for my ph rising from 7.5 to 8.5 in 48 hours that i can find. and as for readings and not colors, i'm not sure how to read the kh and gh. the api instructions aren't that good. but like i said it took next to no drops to do the color change for gh. and 25-28 drops for kh - and the kh is what i'm trying to understand. at the back of the instructions it only goes up to 12 drops and it doesn't say for gh of kh.

 

[raptorrex]

CO2 is incredibly unstable when dissolved in water and will gas of very quickly with surface agitation

indeed, but not when sat in a bucket, with no agitation.

you're right. co2 will lower it. hence when water comes out of my tap and sits for a while, the co2 gasses off slowly and ph rises. that's the only explanation for my ph rising from 7.5 to 8.5 in 48 hours that i can find. and as for readings and not colors, i'm not sure how to read the kh and gh. the api instructions aren't that good. but like i said it took next to no drops to do the color change for gh. and 25-28 drops for kh - and the kh is what i'm trying to understand. at the back of the instructions it only goes up to 12 drops and it doesn't say for gh of kh.

if the CO2 "gasses off", lol. the ph will not rise, or should not. it will simply stop falling.

 

[timbruun]

Well what other explanation is there for pH going from 7.5 to 8.5 over 48 hours? And what about my KH and GH tests? I am going to try and return my test kit and get a new one in case this one is old.

 

[Curiosity101]

The CO2 WILL gas off with no agitation. It only stays dissolved when the water is in the pipes as the water is under pressure.
As soon as that pressure is relieved CO2 begins to gas off, albeit a bit slow than with surface agitation.

This DOES lead to an increase in pH

Having said that...I don't understand what the original question was lol

 

[timbruun]

lol. My main question was how to read the KH and GH tests. And perhaps I'm doing them wrong since it took from 25 to 30 drops for the KH to change and 1-5 or so to make the GH turn green. But the GH was never orange to start.

 

[Curiosity101]

Well I haven't used them myself, but I found this on a forum. It was an answer to someone asking for the instructions because they had lost them.

Directions for testing KH

1. Rinse clean test tube with water to be tested
2. Fill to line with 5 ml water
3. Add Carbonate Hardness Test Solution, one drop at a time, holding dropper bottle upside down in a completely vertical position to assure uniformity of drops. After first drop is added, solution will turn blue. If the water sample contains only 1 degree dKH, the solution will turn from clear to its yellow endpoint after the first drop is added.
4. Cap the test tube and invert several times after each drop. Keep count of the drops being added.
5. The test is completed when the water in the test tube, after having been shaken, turns from blue to bright yellow.
6. Each drop is equal to 1 degree dKH or 17.9 ppm KH.

Directions for testing GH

1. Rinse clean test tube with water to be tested
2. Fill to line with 5 ml water
3. Add General Hardness Test Solution, one drop at a time, holding dropper bottle upside down in a completely vertical position to assure uniformity of drops. After first drop is added, solution will turn orange. If the water sample contains only 1 degree dKH, the solution will turn from clear to its green endpoint after the first drop is added.
4. Cap the test tube and invert several times after each drop. Keep count of the drops being added.
5. The test is completed when the water in the test tube, after having been shaken, turns from orange to green.
6. Each drop is equal to 1 degree dGH or 17.9 ppm GH.

Are you doing exactly as it says above? And it is the API one you are using?

 

[Bignose]

if the CO2 "gasses off", lol. the ph will not rise, or should not. it will simply stop falling.

boboboy, you are incorrect in this. Water companies very often add excess CO2 to the water so that the water will be more acidic than it would otherwise be. This helps reduce the amount of sedimentation and lime scaling that can occur in pipes. This excess CO2 will depress the pH, and as the water sits there, that excess CO2 will go into the atmosphere. Overnight is about all as long as it takes. Nature will always tend towards an equilibrium -- excess CO2 dissolved in the water will tend toward the equilibrium where that excess goes into the air. As that CO2 leaves the water, the pH will indeed rise -- there is less acid in the water, in this case HCO3-, carbonic acid.

About 1 pH unit is typical for the dissolved CO2 that water companies add.

 

[timbruun]

@ curiosity - I am doing exactly as it says there and it is the api test kit that I have.

And in regards to the water, i have well water. Living on a farm so no water company.

 

[raptorrex]

if the CO2 "gasses off", lol. the ph will not rise, or should not. it will simply stop falling.

boboboy, you are incorrect in this. Water companies very often add excess CO2 to the water so that the water will be more acidic than it would otherwise be. This helps reduce the amount of sedimentation and lime scaling that can occur in pipes. This excess CO2 will depress the pH, and as the water sits there, that excess CO2 will go into the atmosphere. Overnight is about all as long as it takes. Nature will always tend towards an equilibrium -- excess CO2 dissolved in the water will tend toward the equilibrium where that excess goes into the air. As that CO2 leaves the water, the pH will indeed rise -- there is less acid in the water, in this case HCO3-, carbonic acid.

About 1 pH unit is typical for the dissolved CO2 that water companies add.

ok thanks for the correction. but how will it go up? the acid has already entered the water. surely removing the CO2, assuming the PH is stable, will have little or no effect. i can see, if the CO2 is replaced by O2, the PH can go up. can i assume that the water buffering, replaces Co2 with O2, to return the water to its "natural" ph?

 

[Curiosity101]

The CO2 in solution becomes the acid. As the water returns to equilibrium (as it's no longer under pressure in the pipes), the CO2 leaves the water.
So basically CO2 + H2O = H2CO3 (carbonic acid), the water does it's best to buffer this, but can only buffer so much.
When the CO2 leaves the acid returns to being H20 and so the liquid becomes more alkaline

And buffering works in two ways, 'soaking' up H positive ions that make solutions acidic. Or adding to the OH negative ions that give you an acidic solution.
So you are right, it will return to it's 'natural' pH when left to stand. But unless we are talking about RO water then it's 'natural' pH is unlikely to be a pH of 7.

Hope that makes sense...

 

[timbruun]

anyone about the kh and gh?