Oclt is overrated

[Lemonhead]

I hate to complain when everyone here has been very helpful. But when doing the oclt test I wanted to be sure my numbers were right so I did multiple fc tests and they come back different every time. The difference was more than 1ppm so the oclt test is invalid imo. I was getting between 20 to 24 drops. After testing 5 times and getting 5 different results I decided to save my reagent.

 

[duraleigh]

Accuracy of the test works for thousands and thousands of people

What do you describe as the end point for that test, please

 

[RMcGirr83]

The OCLT is a method to determine something. If the only two things that consume chlorine are sunlight and organic matter how could the OCLT possibly be invalid if the method itself is performed correctly?

 

[crimson avenger]

I hate to complain when everyone here has been very helpful. But when doing the oclt test I wanted to be sure my numbers were right so I did multiple fc tests and they come back different every time. The difference was more than 1ppm so the oclt test is invalid imo. I was getting between 20 to 24 drops. After testing 5 times and getting 5 different results I decided to save my reagent.

The error of the test is 10%, which is consistent with the results you’re getting. This is not an often-discussed issue in this forum. I had to do some digging myself when I was getting wildly different results for my first SLAM, above 10 ppm.

 

[Dtkokay]

I hate to complain when everyone here has been very helpful. But when doing the oclt test I wanted to be sure my numbers were right so I did multiple fc tests and they come back different every time. The difference was more than 1ppm so the oclt test is invalid imo. I was getting between 20 to 24 drops. After testing 5 times and getting 5 different results I decided to save my reagent.

You're actually raising a complaint about the actual chlorine test, not the OCLT. The chlorine test is just a way to measure chlorine, but that doesn't mean the OCLT test itself isn't valid.

The chlorine test is not going to be 100% repeatable for many reasons. Someone above said the test has a 10% margin of error. That's in line with what you're experiencing.

Also, how do you know you're putting in EXACTLY 10 ml of water every time? That's a very small volume of water to get right every time. You could use a 25 ml sample instead, which would be easier for repeatability, but you would use way more powder and reagent.

And more fundamentally, there accuracy and repeatability are two entirely different issues when it comes to testing, which is a whole other topic. But I suspect what you describe involves both.

 

[setsailsoon]

Maybe try a sample sizer? Works pretty well for me. Seems like it would at least improve repeatability and perhaps accuracy.

 

[Msch99]

Yup. Love my sizer and my speed stir. Both helped me be more consistent with my tests.

 

[RMcGirr83]

Maybe try a sample sizer?

Que es?

 

[Wobblerlorri]

Que es?

Sample Sizer Measuring Tool-*does NOT work with TF-Pro or TF-100 cylinders, only Taylor 9198

tftestkits.net

 

[Lemonhead]

I’ll try the sample sizer .

 

[Lemonhead]

End point of the test is when the pink water turns clear again. At least that’s what I try. It’s not an exact science if your off after testing repeatedly. Therefore the overnight test leads to inaccurate results no ?

 

[Wobblerlorri]

All these tests are dependent on the tester's ability to count drops and recognize color changes. If you're having problems, it's most likely operator error.

 

[lager1829]

Sample Sizer Measuring Tool-*does NOT work with TF-Pro or TF-100 cylinders, only Taylor 9198

tftestkits.net

Or a 60ml veterinary syringe. < $2.00

 

[tim5055]

End point of the test is when the pink water turns clear again. At least that’s what I try. It’s not an exact science if your off after testing repeatedly. Therefore the overnight test leads to inaccurate results no ?

Actually, if the test is performed correctly, yes it is an exact science.

The end point is when it turns clear the first time, not clear "again". If left to sit, a sample will almost always turn pink again. If you are adding more drops at this point we have forun your error.

 

[duraleigh]

Well, pretty close but the way to get a precise endpoint is to continue to add drops until the last drop you add results in NO FURTHER color change....none......nada. That may help a bit.

 

[Lemonhead]

It’s not operater error. Im not doing anything wrong

 

[Lemonhead]

When I say clear again is because it’s clear to begin with

 

[Lemonhead]

Wow you guys are really defensive over the chlorine test. I was just stating what happens if you take the test back to back to back.
You’ll get 3 different readings. No need to tell
Me im
Doing it wrong . I can see color change . I can count . I can read 10ml line on glass.

 

[mknauss]

This thread has found the end.

I am closing it.