Hanna Instruments KH Checker - Inconsistent Readings!

[ytro82]

So I have been using my Hanna KH Checker for roughly a year and been happy with it. I just ordered 2 reagent bottles to hold me over for a while. Both bottles had the same expiration date and lot #. I tested each one to make sure they were giving me the same results. I tested using the same cuvette (properly cleaned) and got a measurement of 6' kh and another reading at 7' kh. I was shocked to see them have different readings, so I tested again and got the same results.

I called Hanna today and they told me to get the 'HI772-11 Alkalinity Calibration Check Set' ($20.00). Being that I've spent close to $75 on the unit and refills, I'm not exactly thrilled about spending another $20. From what I can tell it isn't a problem with the unit - the problem lies in the reagent.

From BRS 'HI772-11' review:
"Great if you want to test the accuracy of your colorimeter, but considering the error in the Hanna dkh checker is almost always in the reagent (which this does not test for), this is not very useful. I've had the dkh be off by more than 1 dkh between reagent batches, but this won't help with that."

I pretty ticked off spending that much $$ on trying to get the best hobby-grade test kit possible and come to find out it's not as error free and I was expecting. Now I don't even know what to do.

Any thoughts on this??

 

[saltyhog]

Interesting. I find their calibration kits to be worthless....at least the ones I've ordered, simply because the standard is far removed from the expected range of the samples I will be testing.

That said, I have the PPM alkalinity checker and my results are remarkably consistent....within 1 ppm most of the time and many times no difference. I wonder if you have a bad reagent bottle (an issue in the remote past but one I haven't encountered in a long time).

 

[EmptyWallet]

I use the copper HR and was happy with very consistent and accurate readings. Then 2 weeks later I'm getting inaccurate and inconsistent readings which is annoying to say the least! Not sure if I have a bad batch of reagent (it doesn't seem to dissolve without heavy shaking now) or its because I'm not using their brand of cleaning agent?

 

[Reefltx]

So I have been using my Hanna KH Checker for roughly a year and been happy with it. I just ordered 2 reagent bottles to hold me over for a while. Both bottles had the same expiration date and lot #. I tested each one to make sure they were giving me the same results. I tested using the same cuvette (properly cleaned) and got a measurement of 6' kh and another reading at 7' kh. I was shocked to see them have different readings, so I tested again and got the same results.

I called Hanna today and they told me to get the 'HI772-11 Alkalinity Calibration Check Set' ($20.00). Being that I've spent close to $75 on the unit and refills, I'm not exactly thrilled about spending another $20. From what I can tell it isn't a problem with the unit - the problem lies in the reagent.

From BRS 'HI772-11' review:
"Great if you want to test the accuracy of your colorimeter, but considering the error in the Hanna dkh checker is almost always in the reagent (which this does not test for), this is not very useful. I've had the dkh be off by more than 1 dkh between reagent batches, but this won't help with that."

I pretty ticked off spending that much $$ on trying to get the best hobby-grade test kit possible and come to find out it's not as error free and I was expecting. Now I don't even know what to do.

Any thoughts on this??

You mentioned using the same cuvette, did the allow it to dry after cleaning?

I have had experiences with bad batches of reagent as well, but mainly having some type of particles floating within the reagent.

 

[Rpc07]

Just to make sure there is nothing in my cuvette I always rinse it with tank water twice before doing the test.

 

[EmptyWallet]

I think my issue is that the reagent powder is not dissolving properly (after 30 seconds of heavy shaking following the 15 seconds of gentle as per instructions) and still seeing 'floaties' of reagent in the bottle. I did a few more tests waiting 1 minute or so for the floaties to settle on the bottom and it seemed to be more accurate and consistent...