Alkalinity issues
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ccombs
Valuable Member
Just a theory- I had a similar issue of Alk tests reading wrong (like way wrong) when neared the extremes of the highs. I was getting tests telling me my dKH was 20.
This being said, we tend to think of these readings as a static progression. Like this, slope stays constant.
In reality I theorize that that these readings might not have an equal slope and might look something more like an exponential graph. (It wouldn't be exponential, but something that does not have a 1:1 rise/run.
Meaning that a slight discrepancy in a test kit at the extreme highs and lows might only be a few percentages off, but appear to be a huge misreading.
Disclaimer- I have not studied this thoroughly, it is just my working hypothesis and I could be way wrong, I have just seen this anecdotally on the web and in my own experience.
All this to say-a higher resolution test kit might be required. You Alk is probably on the lower end (not as low as the readings), just outside of the 'sweet spot' for the test so when the test is off just a little from a percentage standpoint, you are getting low readings.
Your tank would not look like it does if your dKH was that low.
Edit-Attached is a double exponential graph. This is what I think our testing actually looks like graphed out. Middle area is high resolution sweet spot, outer areas get weird.
This being said, we tend to think of these readings as a static progression. Like this, slope stays constant.
In reality I theorize that that these readings might not have an equal slope and might look something more like an exponential graph. (It wouldn't be exponential, but something that does not have a 1:1 rise/run.
Meaning that a slight discrepancy in a test kit at the extreme highs and lows might only be a few percentages off, but appear to be a huge misreading.
Disclaimer- I have not studied this thoroughly, it is just my working hypothesis and I could be way wrong, I have just seen this anecdotally on the web and in my own experience.
All this to say-a higher resolution test kit might be required. You Alk is probably on the lower end (not as low as the readings), just outside of the 'sweet spot' for the test so when the test is off just a little from a percentage standpoint, you are getting low readings.
Your tank would not look like it does if your dKH was that low.
Edit-Attached is a double exponential graph. This is what I think our testing actually looks like graphed out. Middle area is high resolution sweet spot, outer areas get weird.
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dannyab84
Active Member
I’m taking a sample to my LFS now.
Combs that is some good info, I have a Hanna checker which I just need a refill for. I will order it ASAP.
Will have the results from my LFS soon. I’ll keep you guys posted and can’t thank everyone enough for the help.
Combs that is some good info, I have a Hanna checker which I just need a refill for. I will order it ASAP.
Will have the results from my LFS soon. I’ll keep you guys posted and can’t thank everyone enough for the help.
Mjrenz
2500 Club Member
That's a very interesting hypothesis of a hypotenuseJust a theory- I had a similar issue of Alk tests reading wrong (like way wrong) when neared the extremes of the highs. I was getting tests telling me my dKH was 20.
This being said, we tend to think of these readings as a static progression. Like this, slope stays constant.
In reality I theorize that that these readings might not have an equal slope and might look something more like an exponential graph. (It wouldn't be exponential, but something that does not have a 1:1 rise/run.
Meaning that a slight discrepancy in a test kit at the extreme highs and lows might only be a few percentages off, but appear to be a huge misreading.
Disclaimer- I have not studied this thoroughly, it is just my working hypothesis and I could be way wrong, I have just seen this anecdotally on the web and in my own experience.
All this to say-a higher resolution test kit might be required. You Alk is probably on the lower end (not as low as the readings), just outside of the 'sweet spot' for the test so when the test is off just a little from a percentage standpoint, you are getting low readings.
Your tank would not look like it does if your dKH was that low.
Mjrenz
2500 Club Member
Your theory really does make sense, refractometers, pressure guages and most all testing instruments are more accurate at normal ranges. It sounds logical that our test kits would behave similarlyJust a theory- I had a similar issue of Alk tests reading wrong (like way wrong) when neared the extremes of the highs. I was getting tests telling me my dKH was 20.
This being said, we tend to think of these readings as a static progression. Like this, slope stays constant.
In reality I theorize that that these readings might not have an equal slope and might look something more like an exponential graph. (It wouldn't be exponential, but something that does not have a 1:1 rise/run.
Meaning that a slight discrepancy in a test kit at the extreme highs and lows might only be a few percentages off, but appear to be a huge misreading.
Disclaimer- I have not studied this thoroughly, it is just my working hypothesis and I could be way wrong, I have just seen this anecdotally on the web and in my own experience.
All this to say-a higher resolution test kit might be required. You Alk is probably on the lower end (not as low as the readings), just outside of the 'sweet spot' for the test so when the test is off just a little from a percentage standpoint, you are getting low readings.
Your tank would not look like it does if your dKH was that low.
Edit-Attached is a double exponential graph. This is what I think our testing actually looks like graphed out. Middle area is high resolution sweet spot, outer areas get weird.
Randy Holmes-Farley
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Just a theory- I had a similar issue of Alk tests reading wrong (like way wrong) when neared the extremes of the highs. I was getting tests telling me my dKH was 20.
This being said, we tend to think of these readings as a static progression. Like this, slope stays constant.
In reality I theorize that that these readings might not have an equal slope and might look something more like an exponential graph. (It wouldn't be exponential, but something that does not have a 1:1 rise/run.
Meaning that a slight discrepancy in a test kit at the extreme highs and lows might only be a few percentages off, but appear to be a huge misreading.
Disclaimer- I have not studied this thoroughly, it is just my working hypothesis and I could be way wrong, I have just seen this anecdotally on the web and in my own experience.
All this to say-a higher resolution test kit might be required. You Alk is probably on the lower end (not as low as the readings), just outside of the 'sweet spot' for the test so when the test is off just a little from a percentage standpoint, you are getting low readings.
Your tank would not look like it does if your dKH was that low.
Edit-Attached is a double exponential graph. This is what I think our testing actually looks like graphed out. Middle area is high resolution sweet spot, outer areas get weird.
I have no idea what you are referring to or how this might relate to low alk.
Alk is linearly related to the titrant used to get to the endpoint. It reads perfectly well at low alk or high alk.
Randy Holmes-Farley
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Randy Holmes-Farley
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My Tank Thread
Are you reading the syringe backwards? That's a common issue. Your wife may as well.
If you used a large fraction of a syringe, that's a lot of alk.
ccombs
Valuable Member
It was simply a theory that the tests are not linear when you get to extreme highs and lows when dealing with hobby grade kits. If this is incorrect I am more than happy to admit I am wrong, It was just a hypothesis.
Randy Holmes-Farley
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Alkalinity is linear with titrant added. If the volume used is so small that it is hard to measure accurately, certainly that will cause an unusually high percentage error. Otherwise, the encountered extremes are not generally an issue with an alk kit.
ccombs
Valuable Member
Thanks! Sorry if I did not make it clear enough that it was just a theory, not fact. I don't care if my theories are right or wrong, I am just looking for the truth haha.Alkalinity is linear with titrant added. If the volume used is so small that it is hard to measure accurately, certainly that will cause an unusually high percentage error. Otherwise, the encountered extremes are not generally an issue with an alk kit.
Science is awesome!
rushbattle
Valuable Member
I think you might be reading the syringe backwards, like others have pointed out. Can you try again testing alk while carefully reading the instructions?
Mjrenz
2500 Club Member
Watch that whole video I posted earlier, that guy describes the testing procedure with the salifert kit pretty well in my opinion
Mjrenz
2500 Club Member
You made it clear , it's the first thing you said in your post, but now we know
PatW
2500 Club Member
And if you cannot get a reading close to 11.5 from following the video, go to you tube and find another video.
Or go to the LFS and have that person observe you when you test. You probably inverted something. But once one locks up on something like that, it can be hard to auto correct.
