Is it normal to see huge swings in FC/CC?

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I did not see your video until now...that does look like you need more powder at the beginning since it did not turn very bright pink nor did it change fast. My experience is once you get enough powder in it should be fairly dark pink to start with.

I think it is possible you may have a very high TC level.

Could you test your water with the OTO chlorine test (the one attached to the ph test) and post the color (or a picture). The OTO test is not accurate but it will give a sense for how high the chlorine level actually is.
 
Will try. Did some math...pool opened on may 18. That's 12 days of shocking...some days not very attentive. Pool was very dirty and green when opened. So far, I've put 13 gallons of 10%bleach and 4 lbs of 73% cal-hypo. Pool opened with zero FC.

Pool calculator tells me that for my pool size that is roughly 57 ppm chlorine over the 12 days. Doesn't seem like that much, or is it? We've had plenty of sunny days and my cya is low.
 
That is not a lot of bleach (and calhypo) for a pool your size when fighting algae and/or ammonia.

Early on we talked about testing for ammonia, you might want to do that just in case you have it and if you have a lot then at least you will be able to ballpark how much more chlorine you will will need.
 
I might not be able to get to the store for an ammonia test for a couple of days. It's on my "to do" list though.

Ran the morning tests about 1 hour after sunrise.

FAS-DPD test results (I used 2 large scoops and another half scoop of powder for good measure.):

FC=13
CC=5

My last test from last night (with 2 scoops) read FC=18, CC=5. So, if I trust my results (I don't!) I lost 5 ppm FC overnight without gaining any ppm CC. That is at least in the realm of possibility. Remember, I did not add a single drop or granule of anything to the pool yesterday.

Also, I did the OTO test this morning. Photo below. Based on this result, I did not add anything to the pool this morning. If my result is to believed, I still have above shock levels of chlorine.
 

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Okay, the OTO test tells us that you are not excessively high in TC (TC =FC+CC)...I was expecting it to be higher. By the way, the OTO chlorine test really only goes up to 5 ppm accurately, the color I am seeing suggests you could be in the 5-15 ppm TC...which is at least in the ballpark your total of 18 ppm as measured with the fas-dpd test.

Did you still get the weak pink color upon adding two scoops of powder this morning? Did you still get a quick return of pink (in a couple of seconds) after turning clear like the video you shared?
 
I very well may have been excessively high yesterday if I am still up to 15 ppm FC without having added any chlorine in 36 hours.

I did get the weak color at first. So I topped it off with a 3rd scoop. I let the magnetic stir work its magic for about 10 seconds and got a solidly bright pink. I wouldn't call it intense though. At least not as intensely pink as I get when I add the R-0003.

While doing the FAS-DPD test, it initially turned clear around 10 ppm FC, I stopped for maybe 3 seconds and a light pink reappeared (magnetic stir going the whole time). I started adding R-0871 again fairly slowly this time and got to 13 ppm and then it stayed clear.
 

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Ran 3 more tests. Used 3 scoops of powder. I have not added any chlorine all day.

1st test (solution would turn clear around 8ppm, then maybe 3 seconds later get the slightest hint of pink. SO I kept going until the clear held for 10 seconds.):
FC = 15, CC=1.5

2nd test:
FC = 8, CC=12

3rd test:
FC = 7.5, CC=8.5

On the 2nd and 3rd test, I ignored any color changes after the solution turned clear, even if the color turned ever so slightly back to pink after 5 seconds.

Remember that my test this morning was FC=15, CC=7. We had a very sunny day and my CYA is 20.
 
Ran a 4th test and got FC = 15, CC = 1.5 again (same as 1st test).

So, if I add R-0871 until the solution STAYS CLEAR for 10 SECONDS, that's my result. I get a much different result (FC closer to 7.5) if I don't wait the 10 seconds for the solution to return to pink.

So which method is correct? I know the testing instructions say the solution may return to pink after a minute. But what about 5-10 seconds? What is the rule of thumb?

Thanks for all the help. I'm at wits end but I appreciate the tips and time everyone on this board takes with us newbies. Must be as frustrating for you as it is for us!
 
One possibility that I've run into:

When my hands were dirty/oily/sweaty, the gunk was transferred to the speed stir bar, which resulted in a high CC reading during that test. I then washed my hands real good and re-did the test and there was no CC.

Just a thought, but is there anything that could possibly be contaminating your water sample?
 
The only thing contaminating it that I can think of is the pool/spa itself. Excellent theory though...I'll keep my eye out for something like that.

So far the leader in the clubhouse is "CC bleed through due to extremely high CC caused by ammonia".

I might be the only person on the face of the earth hoping their ammonia test comes back positive. If not, i'm left to comclude that i lack the wherewithal to perform the simple test! I'll likely know tomorrow.
 
linen said:
I not entirely sure, but I am suspecting your CC is very high and that it is "bleeding through" during the test for FC. I would think not waiting is the right approach if this is CC "bleeding through"

Take a look at these posts about a similar situation here:
http://www.troublefreepool.com/chlorine-test-confused-t11803.html#p94875
http://www.troublefreepool.com/need...d-maintaining-shock-level-t45352.html#p369305

I do think it would be useful to have an ammonia test done.
Click to expand...

Those were helpful links. The stories about the CC "bleed through" do sound like what I am experiencing. One thing I haven't mentioned is that once I am done with the CC test, I never get a return to pink. It is only on the FC test. So from now on, I think I will stop and record FC based on when the solution first turns clear. Not when it turns clear for "more than 10 or so seconds." Unless that is, someone advises differently!

Here's the latest test results...
If you trust my results from about 7 PM earlier today (again, I don't), I had either FC=15/CC=1.5 or FC=7.5/CC=8.5. I put a gallon of 10% into the pool at 7.

At 11 PM, I just tested and using the method I think is correct, I get FC=12.5, CC=18.5.

This still makes no sense to me as I don't see any way to get from either test result at 7 to the result I just got after adding only 1 gallon of chlorine.

I'll try to stop at the pet store and pick up an ammonia test tomorrow.
 

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