Correct wait time during CYA test?

[modog]

Hello Everyone,

I use the recommened TF test kit and had a few questions. When conducting the CYA test, I mix the bottle, wait AT LEAST 30 seconds and then mix again and test. With that said...

1) If I wait exactly 30 seconds, I get a read of 35. If I wait around 2 minutes, I get a read of 65. Is there a direct relationship between the wait time and the reading? Which one is accurate?

2) When dispensing into the reading tube, I usually let the stream glide down the wall of the tube instead of directly dropping it into the middle of the tube. Is there a difference as I noticed it clouds up less when I dispense down the side of the tube?

3) After dispensing, is there a time limit to wait before I should read? Also, is there too long a time limit before the read is inaccurate?

4) I have based my entire summer off the 35 reading and kept my CH at 5ppm with no issues. Is 35 too low?

Thanks,

MoDogg

 

[Bama Rambler]

As long as the reagent is well mixed in the sample time (within reason) shouldn't matter.

I use the speed-stir and once I've done testing it I pour it out so I haven't tried it after a few minutes. I'll have to try that the next time I test it.

Since you're obviously not having a problem I'd stick with what's working.

 

[modog]

Ok thanks. Just wanted to know if anyone else has come across this before.

 

[duraleigh]

If I wait exactly 30 seconds, I get a read of 35. If I wait around 2 minutes, I get a read of 65.

This part puzzles me. I do not experience that nor have I heard any other reports of that. You should be able to get the same results regardless of the time. It has been my experience that even 10 minutes apart doesn't matter.

Was that a one time event or do you find that to be the case repeatably?

 

[JasonLion]

Extra time is usually only important when the water sample is fairly cold. Cold slows the reaction time, so the cloudiness takes longer to form.

Pouring down the walls of the tube leads to fewer air bubbles, which is good. Air bubbles, though rare, can interfere with the test.

 

[modog]

I will test again this week and repost my results of whether time affected the readout.