Strange test results -- very high combined chlorine (CC)

[Themadczar]

I am mostly just venting/complaining... But i truly don't understand why I'm maintaining 4-5ppm fc while cc is also staying in the high teens. The bucket test might tell me when to expect the light at the end of he tunnel but it doesn't get me there any quicker. I suppose I will just keep plugging away...
As for CYA, poolcalc says I should have 23ppm, but I haven't tested since right after adding the dichlor. Should I do so now? And the pool is covered most of the time. It's an auto-cover, but without a fence I have to keep it closed when I'm not around (neighbor has a toddler). I have been trying to leave it open as much as possible though.
Getting to Sam's is not easy, and I still have 19 lbs of dichlor. Until I can get the trichlor, what do you recommend? And how does putting trichlor run higher CL through pipes/filter but not the pool?
And thanks for all the help!

[Themadczar]

Ok, based on BigDave's questions, I included cya in my testing tonight. Riddle me this... How could I have no measurable cya in the pool when I first tested it, then the only cya added was in the 5# of dichlor I put in a few weeks ago which amounts to about 23ppm. Now my cya is over 50ppm. Where did the other 27 ppm come from?
I am assuming that the higher than expected cya number explains why chlorine levels are not dropping much during the day when I have been able to keep it uncovered... For example, last night I had 5ppm fc and 19ppm cc, but tonight after leaving the cover off all of today and it being a bright, sunny day, fc was 4.5 and cc was 15.5 (i didn't add anything last night after testing).
So now, if I understand correctly, i should take my tc up to 30ppm (by adding 8-9 qts of 6% bleach), right?

[PoolDoc]

I don't have answers to all your questions, but I'd caution you not to go to FC>30 ppm with a vinyl pool, when your CYA levels are doubtful.

If you want a more trustworthy CYA test, take a open glass container (1 qt measuring cup?), fill it with pool water, and set in the sun. After the chlorine level (TC) is below 3ppm, use the sample to test for CYA and see what you get.

[Themadczar]

I appreciate the honesty. And I will work on the cya test today. To add to my confusion... I tested the water today and fc was 3.5, cc was 17.5. No surprises there. But when I checked tc with my oto kit, it was about 2 (definitely not as dark yellow as the 3ppm color). I have never seen my oto kit go higher than 2, but I know my tc is over 20. Is the reagent bad? It's a new kit early this season.

[PoolDoc]

DPD FC + CC *should equal* OTO after 10 minutes.

Might want to check that. If not, we've got a mystery we need to look into.

[Themadczar]

Not sure I'm following you... Do you mean I should read the oto test after 10 minutes and that should give a tc reading that will match immediate dpd results?
Also, I don't know if this adds another piece to the puzzle or confuses things further, but I just tested the CL again about an hour after adding 192oz of bleach. I pulled a sample from the pool in a measuring cup like I always do and ran the same dpd test 4 times with 4 completely different results:
1. Fc 5, when I added r-0003 for cc the sample turned a light yellow, not pink. I have had this happen once before, so I retested (assuming I did something wrong)
2. Fc 22, cc 1.5... Huh? Retest again...
3. Fc 7, cc light yellow/peach????
4. Fc 15, cc 7
All 4 tests were done within minutes from the same sample of pool water, and I rinsed with filtered water between tests. This stuff should be pretty simple, and I'm a pretty smart guy, but I am completely lost here.

[Themadczar]

Not sure I'm following you... Do you mean I should read the oto test after 10 minutes and that should give a tc reading that will match immediate dpd results?

If I got that correct, then after waiting 10 min, the oto test was definitely darker yellow than the 3ppm mark (the highest on my test) but not by much... I would think 20ppm or so would be much darker yellow or brown, but maybe I'm wrong.

[waterbear]

Not sure I'm following you... Do you mean I should read the oto test after 10 minutes and that should give a tc reading that will match immediate dpd results?
Yes
Also, I don't know if this adds another piece to the puzzle or confuses things further, but I just tested the CL again about an hour after adding 192oz of bleach. I pulled a sample from the pool in a measuring cup like I always do and ran the same dpd test 4 times with 4 completely different results:
1. Fc 5, when I added r-0003 for cc the sample turned a light yellow, not pink. I have had this happen once before, so I retested (assuming I did something wrong)
DPD bleachout caused by high chlorine levels
2. Fc 22, cc 1.5... Huh? Retest again...
Probably close to what your levels actually are but still bleaching out a bit.
3. Fc 7, cc light yellow/peach????
DPD bleachout caused by high chlorine levels!
4. Fc 15, cc 7
All 4 tests were done within minutes from the same sample of pool water, and I rinsed with filtered water between tests. This stuff should be pretty simple, and I'm a pretty smart guy, but I am completely lost here.

Try diluting a sample of pool water with an equal amount of distilled water and testing that with the FAS-DPD test and multiply that test results by 2 to see what you get.
Re: the autocover...are you leaving the pool uncovered? If a pool is kept covered it is not uncommon for there to be a persistent high CC problem since there is limited offgassing of the disinfection byproducts and exposure to sunlight also is an integral part of the process of destroying CC (which is why persistent CC is a problem in most indoor pools!)