Is it normal to see huge swings in FC/CC?
- Thread starter brian4110
- Start date
Oh, I trust Dave for sure and his kit. In fact, I will be buying more reagent soon with all this testing!
It's the pool I'm starting to regret.
It's the pool I'm starting to regret.
For those following along or who have a similar problem, Dave has convinced me that the lower FC numbers are correct. That is, as soon as the solution flashes clear, I am done or almost done with the FC test. This makes sense based on my OTO result as well.
For now I've decided to continue trying to shock based on the method of testing Dave advised. I'm going to ignore CC until I can hold FC because it is going to be astronomical while I fight the ammonia. My fingers are crossed.
For now I've decided to continue trying to shock based on the method of testing Dave advised. I'm going to ignore CC until I can hold FC because it is going to be astronomical while I fight the ammonia. My fingers are crossed.
I wanted to provide some closure for anyone who might run into a similar problem in the future and as payback for all the kind folks who helped me in this thread.
Problem: I was having difficulty with the shock process because I could not determine my FC levels because during the FC portion of the FAS-DPD test my solution would flash 'clear' but then turn back to pink before I could start the CC test.
Solution: Based on advice from duraleigh (Dave), the FC test is done or almost done when the FC flashes clear. At most, you should add 2-3 more drops to see what happens but in most cases you can consider the FC test to be done and record your result for FC even if the solution turns to pink after a few seconds. Some testing instructions you might find say that the solution will return to pink if you wait for a minute or more. What I was seeing was a return to pink after less than 10 seconds.
What was happening? Well, it turns out I had an extreme but unknown ammonia problem. This was causing me to have extremely high CC readings (somewhere in the 20s ppm) because I wasn't adding chlorine quickly enough to break down the unexpected rise in CC. I was trying to perform the shock process by adding the pool calculator amount of chlorine. I would wait 1 hour then retest. However when I'd retest, the FC levels were actually way lower than I was expecting because I didn't realize that ammonia was consuming the chlorine almost immediately. So I'd add 10-12 ppm chlorine, only to test in an hour and find that my solution would flash clear after only 5-6 drops. In fact, the FC was combining with the ammonia in such a way that the CC number was skyrocketing, causing the difficulty in the FAS-DPD test by turning the solution back to pink without the need to add the R-0003 reagent for the CC test. I believe some folks refer to this as the CC 'bleeding through' on the FC test. I wasn't trusting my results because I didn't have enough experience with the test to know how to read the strange results.
Once I realized that the FC result should be recorded when the solution flashes clear, it became much easier to determine how much chlorine I needed to add. This, along with frequent testing and an ammonia test, made it obvious just how quickly and why my FC was being consumed. I've since been able to keep my CC down by maintaining a shock appropriate level of FC and my ammonia problem is almost gone.
So word to the wise for any newbies out there...if you are running a FAS-DPD test, and your solution flashes clear but just won't stay that way for more than a few seconds, you probably have an extremely high CC reading. Stop and record your FC right there. Oh, and you might want to go out and get an ammonia test.
Problem: I was having difficulty with the shock process because I could not determine my FC levels because during the FC portion of the FAS-DPD test my solution would flash 'clear' but then turn back to pink before I could start the CC test.
Solution: Based on advice from duraleigh (Dave), the FC test is done or almost done when the FC flashes clear. At most, you should add 2-3 more drops to see what happens but in most cases you can consider the FC test to be done and record your result for FC even if the solution turns to pink after a few seconds. Some testing instructions you might find say that the solution will return to pink if you wait for a minute or more. What I was seeing was a return to pink after less than 10 seconds.
What was happening? Well, it turns out I had an extreme but unknown ammonia problem. This was causing me to have extremely high CC readings (somewhere in the 20s ppm) because I wasn't adding chlorine quickly enough to break down the unexpected rise in CC. I was trying to perform the shock process by adding the pool calculator amount of chlorine. I would wait 1 hour then retest. However when I'd retest, the FC levels were actually way lower than I was expecting because I didn't realize that ammonia was consuming the chlorine almost immediately. So I'd add 10-12 ppm chlorine, only to test in an hour and find that my solution would flash clear after only 5-6 drops. In fact, the FC was combining with the ammonia in such a way that the CC number was skyrocketing, causing the difficulty in the FAS-DPD test by turning the solution back to pink without the need to add the R-0003 reagent for the CC test. I believe some folks refer to this as the CC 'bleeding through' on the FC test. I wasn't trusting my results because I didn't have enough experience with the test to know how to read the strange results.
Once I realized that the FC result should be recorded when the solution flashes clear, it became much easier to determine how much chlorine I needed to add. This, along with frequent testing and an ammonia test, made it obvious just how quickly and why my FC was being consumed. I've since been able to keep my CC down by maintaining a shock appropriate level of FC and my ammonia problem is almost gone.
So word to the wise for any newbies out there...if you are running a FAS-DPD test, and your solution flashes clear but just won't stay that way for more than a few seconds, you probably have an extremely high CC reading. Stop and record your FC right there. Oh, and you might want to go out and get an ammonia test.
brian4110 said:
Thanks for posting this. When people show up with an ammonia problem, they are completely distraught, and your third paragraph should be required reading. Well said.
Also, it seems that there is a bit of a mystery on this board as to what conditions lead to ammonia problems. I bought the pool/house after it was closed, so I can't comment much on it's history. But I can say that upon opening the pool had a lot of dirt/mulch that had blown from poolside in it. There were very few leaves, leading me to believe they closed the pool rather early last year (we have a loop-loc cover). On opening, the water was green but not nearly as bad as some of the neglected swamps I've seen here.
This makes sense to me. If ammonia is the byproduct of bacteria converting the CYA, then this is exactly the kind of condition you would expect leading to an ammonia problem. A pool closed and/or opened in warm-ish weather that ended up with lots of bacteria laden soil in it over the winter. So if you open your pool and find that you have a lot of dirt/mulch in it, you might want to do yourself a favor and test for ammonia. Would have saved myself a TON of frustration if I'd only run that test.
This makes sense to me. If ammonia is the byproduct of bacteria converting the CYA, then this is exactly the kind of condition you would expect leading to an ammonia problem. A pool closed and/or opened in warm-ish weather that ended up with lots of bacteria laden soil in it over the winter. So if you open your pool and find that you have a lot of dirt/mulch in it, you might want to do yourself a favor and test for ammonia. Would have saved myself a TON of frustration if I'd only run that test.
linen said:
The water has been crystal clear for about 48 hours now. In fact, I let the kids take a quick dip last evening (just wading around in the shallow end). Nobody seems any worse for wear. At swim time FC was at shock level and CC was 0.
A week ago the water still had a slight green tint to it, almost as if I had a metals problem...but that has gone away too. One problem I have encountered is that my pH has plummeted from 7.5 to 6.8 or lower. I've got some borax on standby as soon as I am done shocking if I need to raise pH.
I lost about 3 FC last night and had CC=1 this morning. These numbers were inconceivable even 3 days ago. I think I'll pass the OCLT tonight. I still had a trace of ammonia in the pool as of last night which caused that FC loss. But it's nothing like the 10ppm I was losing in an hour when my ammonia level was high.
The ammonia condition in this pool is a VERY unusual condition.......my guess is about a dozen or so we've had reported in 60,000 threads. That does not rise to the level of everyone rushing out to buy an ammonia test when their pool opening is a swamp.
The correct procedure is to run a complete set of tests and then shock your pool. In the VERY VERY unlikely event your pool contains ammonia, your FC will be burnt out much quicker but the solution is still the same....keep adding chlorine until your pool clears.
The correct procedure is to run a complete set of tests and then shock your pool. In the VERY VERY unlikely event your pool contains ammonia, your FC will be burnt out much quicker but the solution is still the same....keep adding chlorine until your pool clears.
duraleigh said:
Yup...listen to duraleigh! I don't want to make it sound like I had a typical condition and cause anyone to run out and waste money on an ammonia test. But if you keep adding chlorine and your tests don't seem to make any sense because YOU KNOW you just put chlorine in and it's suddenly gone and your CCs are astronomical...well then maybe go out and get a cheap ammonia test. It will certainly be cheaper than taking your troubles to the pool store and buying some magic beans!
In any event, the solution is still the same...chlorine. The ammonia test just lets you know how much you might need. And in my case, it was ALOT.
Just wanted to say how thankful I was finding this thread!! I too was having problems with inconsistent results on fc and cc tests. I'd take a large sample of water from the pool and do several tests in a row. While the TC would stay pretty much the same the fc and cc would flip flop and I had no idea which results were correct. Reading this thread saved my sanity!