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

[Themadczar]

I don't get it... Both my fc and cc are staying pretty consistent, but they are still not where they should be. Since getting home from vacation, fc isn't dropping below 4, but cc is staying in the high teens. See below...

Date_ time_ FC_ pH_ CC

2013-06-23_ 00:10_ 5.0_ 7.7_ 18.5
2013-06-23_ 19:05_ 6.0_ 7.7_ 12.5_ added 384oz 6% bleach
2013-06-24_ 18:13_ 4.5_ 7.7_ 19.0
2013-06-25_ 19:42_ 4.5_ 7.7_ 16.0_ added 192oz 6% bleach (1/2 dose since already over 20ppm)
2013-06-26_ 17:38_ 4.5_ 7.7_ 19.5_ added 192oz 6% bleach (1/2 dose since already over 20ppm)
2013-06-27_ 18:58_ 5.0_ 7.8_ 19.0

I can't add more bleach (already over 20ppm tc), but doesn't seem to be making progress either. And ph has creeped up to 7.8. Any idea what I should be doing at this point? This is getting really frustrating. Pool open for over 2 months and we still can't swim in it.

[PoolDoc]

It's a terribly frustrating problem, but one without any easy solution. We had dozens of cases of this, last season after one of the warmest springs on record, and only a handful this year, after one of the coldest springs.

But, since you are one of the few, there's no consolation in that.

It doesn't appear that you have raised your CYA much, and unless you do so, it's risky to run higher chlorine levels. I'd recommended using dichlor, for that reason, but at this point, I believe you'd be better off buying a bucket of 40# of trichlor at Sams Club, and running those in your skimmer. That way, you can run chlorine levels higher than 25 ppm in your pipes and your filter, without running higher than that in the pool. That will add CYA and probably accelerate the decomposition of the the combined chlorine.

We've mentioned a bucket test, several times. If you want to know how much longer, that's the way to find the answer. Otherwise, you'll just have to plug along till it's done . . . whether it takes a week more, or a month more.

The only other practical way to remove the ammonia that I know of is biological -- which would mean allowing your pool to turn to a slime pit for a week or more. You'd have to buy an ammonia test kit, so you'd be able to see when the biological removal of ammonia was complete. And then, you'd have a week or two of clean-up.

You can also do an in-pool drain, if you buy a small sump pump, and a tarp that's 15' larger than your pool in all directions (20' x 50' tarp!). If you are interested, I'll explain.

But I don't know of any easy or pleasant fix.

[BigDave]

Maybe I missed it, but, I don't recall seeing a CYA reading for a while. There was 0 CYA at the beginning of the thread and 5 lbs dichlor added so I'm guessing 20-25 ppm CYA?

Is the pool covered (also sorry if I missed it)?

[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.