TF Test Kit - unable to test FC

[dandan74]

I shocked my pool(14000gal) with 10 gal 6% bleach yesterday to get rid of the algae. When I tested the water last night, the FC reading was 33.
However, when I tried to test the water again this morning, I didn't get any reading. I used TF test kit and followed the instruction.
Filled 10ml pool water and then put a spoon of 870 power. The water turned pink first but quickly became clear again after I shaked to mix.
What exactly this means? Too much bleach or too little?

 

[duraleigh]

More than likely, it means all your FC was consumed killing algae and other organics. You might try the OTO Chlorine test (it's in the blue box) but I think it will confirm your chlorine has been consumed.

You could then check your FAS_DPD chemistry and procedures by putting a couple of drops of bleach in a bucket of water but I doubt it's necessary......it sounds like you are doing it right.....I think your chlorine has simply been used up.

 

[JasonLion]

Try the simpler OTO test. If that one remains clear then you really don't have any chlorine. If the OTO test turns orange, then try the FAS-DPD chlorine test again, but this time add twice as much of the powder to start. Some times at very high FC levels you need to use more of the R-0870 powder to get the sample to stay pink.

 

[duraleigh]

Good thought, Jason.

I should've remembered that!

 

[Guest]

Don't even neeed the OTO test. If the color "flashed" pink and then turned clear it has bleached out and you need to add more DPD powder a scoop at a time until the color holds.

 

[duraleigh]

When I tested the water last night, the FC reading was 33.
However, when I tried to test the water again this morning, I didn't get any reading.

Now, I'm confused. Assuming he/she followed same procedures, why would it work the night before and not now?

 

[dandan74]

Thanks Guys!
Ok. Here is the story, I saw your reply and took some time off work re-testing my pool.
This time, it worked. I don't have to add the second snoop of the 870. It turned pink as usual.
I guess the FC was too high it was just bleached out. The same test working last night was probably due to uneven FC in the pool. I shocked the heck of it. Now my testing shows a little drop of FC:from 33 last night to this afternoon 30, CC from 3 last night to 0.5. My CYA is 60. I am assuming I don't have to add more bleach at this point. How come I still have CC? What does this mean?

 

[Guest]

When I tested the water last night, the FC reading was 33.
However, when I tried to test the water again this morning, I didn't get any reading.

Now, I'm confused. Assuming he/she followed same procedures, why would it work the night before and not now?

Amount of DPD powder added and/or current FC level.

 

[Guest]

It takes time, UV light, and outgassing to fully get rid of the CC.....what you need now is a big bottle of POP (Pool Owner Patience) and apply it liberally to yourself!

 

[JasonLion]

CC at 0.5 can be ignored. The test reads any amount above zero as 0.5. Your actual level is probably quite close to zero. (If you are doing the test so that it reads in steps of 0.2, then you ignore CC levels of 0.2 or lower. When doing the test so that it reads in steps of 0.5, you ignore CC levels of 0.5 or lower.)

CC is measuring a combination of several different forms of combined chlorine. Some of those break down very quickly, and others break down quite slowly. Normally, the great majority of the CC is the kind that breaks down quickly, which is what you have seen happen. There can still be a small residual amount of the kind of CC that breaks down more slowly. It will take more time and lots of sunlight to break down the last little bit of CC. But you don't need to wait for that to happen.