FC vs. CC Test Results

[SeanH]

I took a FC reading earlier today and using the FAS/DPD test it came out to .5.

I was thinking that I could see a greenish tint coming back and that I either didn't get rid of all my alge from a few weeks ago or it came back.

I added 2 182 oz bottles of bleach around 7:00. I did another test around 9:00 and my FC was at 1.

I added 2 more bottles at 9:00 and then tested again about two hours later.

Here are my full numbers:

FC=1.5
CC=5.5
PH=7.2
TA=60
CH=340
CYA=Not Tested

I have been adding 8lbs of CYA over the past few days via a sock in front of a return to get my CYA up from 0 so I did not test it.

Does the CC at 5.5 tell me that there is something (alge?) in the water that the FC is acting on?

Sean

 

[JasonLion]

Yes, with CC that high there must be something in the water that the chlorine is fighting. You should do the full shock process, raise FC to shock level as frequently as practical, up to once per hour, and hold it there till FC holds overnight. Base your shock level on the CYA level you were aiming for until you can get a real CYA measurement.

 

[SeanH]

Most of the history of this post is gone since the upgrade. I did save it. If it would be helpful for searching in the future I can add the text...

Here is where I got with this today...

7:45am
FC=1
CC=.5
Added 2 174oz jugs bleach

8:30am
FC=6
CC=1

9:30am
FC=4
CC=.5
Added 2 174oz jugs bleach

11:30am
FC=5
CC=.5
Added 2 174oz jugs bleach

6:00pm
FC=2
CC=.5
PH=7.0
TA=30
CH=370
Added 2lb baking soda to try to bring TA up some

9:00pm
FC=1
CC=.5
PH=7.0
TA=30
Added 4lb board to try to bring up PH

9:45
Added 1 174oz jug bleach

11:00pm
FC=4
CC=.5
PH=7.0
TA=60

I'm encouraged that the FC only dropped from 5 to 2 from 11:30 to 6:00pm during the sunniest part of the day for me. It's only been 4 days or so since I added the CYA so I'm not sure where that's at yet.

I never got to the pet store for an ammonia test, but given everything I've read compared to what my results were with chorine, I think it's a good possiblity that was the problem.

I'll post the test results from tomorrow early am. Hopefully I can hold a decent FC reading overnight.

Sean

 

[SeanH]

I tested for amonia yesterday, and there was no reading.

I still can't seem to hold a decent chlorine reading overnight.

If I add enough to bring the FC up to 3-5 it will be down to 1 overnight.

Latest results

FC=1.5
CC=.5
PH=7.3
TA=60
CYA=40

Tomorrow I'm going to backwash DE and add some more CYA to bring it up a little.

Not sure if there is much more I can do.

The water is crystal clear. I'm just hope there is nothing wrong that can't be seen and hasn't been tested.

Sean

 

[Guest]

Test your CYA and post the number. The only way you will get rid of the CC and have your FC hold is to start shocking the pool but the ONLY way to know how high you need to shock is to know where you CYA is! (or where you expect it to be from the CYA you already added!). Just trying to keep the FC and 3 is not going to solve the problem. Your pool has a chlorine demand right now and until that is statisfied you will NOT be able to hold FC or get rid of the CC!

 

[SeanH]

Test your CYA and post the number. The only way you will get rid of the CC and have your FC hold is to start shocking the pool but the ONLY way to know how high you need to shock is to know where you CYA is! (or where you expect it to be from the CYA you already added!). Just trying to keep the FC and 3 is not going to solve the problem. Your pool has a chlorine demand right now and until that is statisfied you will NOT be able to hold FC or get rid of the CC!

The CYA is at 40 as posted above. I have not added more yet, but I was going to today.

Most of the history of this post was lost during the site upgrade, so it's not there to view, but the concensus was that the amount of chorine that I was adding was abnormally high given that there does not appear to be any alge.

I was adding 4 174oz jugs of bleach and my readings were FC=1 and CC=2 30-45 minutes later.

There was a though that I had ammonia, but when I tested that it showed that there was none.

One interesting thing to note is that my CYA went from around 80 to 0 over the winter.

Sean

 

[duraleigh]

Sean,

That your pool went from 80 to 0 CYA is not relevant to your current issue. It does indicate the pool had little or no water balance during that time.....but that was then and this is now.

Remember this important fact.

Chlorine is consumed by two things.....

1. Sunlight

2. Organics in your pool

So, it's pretty easy to eliminate the sun from the equation by testing in the evening and then again early the next AM.
If you have FC loss any greater than 1.0 during that overnight period, the conclusion is pretty inescapable.

 

[SeanH]

Sean,

That your pool went from 80 to 0 CYA is not relevant to your current issue. It does indicate the pool had little or no water balance during that time.....but that was then and this is now.

Remember this important fact.

Chlorine is consumed by two things.....

1. Sunlight

2. Organics in your pool

So, it's pretty easy to eliminate the sun from the equation by testing in the evening and then again early the next AM.
If you have FC loss any greater than 1.0 during that overnight period, the conclusion is pretty inescapable.

Dave - This is what you wrote in the original thread on this before the upgrade.....

"I think you may have more than an algae issue. That consumption is very atypical. "

I was under the impression that I was using WAY MORE chlorine than would be needed to get rid of alge.

I guess I could go back to adding 4 174oz jugs every 30-60 minutes with no apparent results, but it didn't seem like that was the correct route. I just didn't want to be wasting time and money if that wasn't the problem.

Thanks for the help. I appreciate it.

Sean

 

[SeanH]

Maybe I'm being overly paranoid now....

Last night my FC was at 1.5 so I added 174oz of bleach at 10:30pm which was for a target of 5.

I just tested (too many things going on for fathers day to test early) at 11:30am and I'm at 3.5. It's sunny out, so maybe some of the loss could be attributed to that?

I do know this is a MUCH better loss than a week ago. To lose 1.5ppm in 12 hours seems ok to me.

I think I'll shock it tonight and see what the results are in the morning.

Again, thanks to everyone that has offered assistance. This has been frustrating because I feel like I have not been able to get ahead of the problem.

Sean

 

[duraleigh]

"I think you may have more than an algae issue. That consumption is very atypical. "

I was under the impression that I was using WAY MORE chlorine than would be needed to get rid of alge.

I still think that, I think that your water was so badly neglected you had ammonia in your pool that was consuming all your chlorine (the loss of all your CYA is a good indicator).

Remember, I also said (I think) that regardless, chlorine (and lots of it) is still the answer.

As I said, go back to the basic premise of "there are only two sources of chlorine loss...sunlight and organics"

 

[Guest]

First, it's not only ammonia that can create a chlorine demand but nitrates also.
second, what was the water like when you got a result of CYA of 40 ppm? Was the water cloudy or green? If so your CYA is actually lower than that so you might just be losing chlorine to sunlight.

 

[SeanH]

First, it's not only ammonia that can create a chlorine demand but nitrates also.
second, what was the water like when you got a result of CYA of 40 ppm? Was the water cloudy or green? If so your CYA is actually lower than that so you might just be losing chlorine to sunlight.

The thing is, for the past two weeks, my water has been 100% crystal clear. Not green or cloudy. If my eyesight were good enough, I could read the words on a quarter in the deep end!

My CYA reading was from yesterday.

Sean

 

[SeanH]

"I think you may have more than an algae issue. That consumption is very atypical. "

I was under the impression that I was using WAY MORE chlorine than would be needed to get rid of alge.

I still think that, I think that your water was so badly neglected you had ammonia in your pool that was consuming all your chlorine (the loss of all your CYA is a good indicator).

Remember, I also said (I think) that regardless, chlorine (and lots of it) is still the answer.

As I said, go back to the basic premise of "there are only two sources of chlorine loss...sunlight and organics"

What would prevent it from being neglected? I use a pool maintenance company to close the pool and they put in a "winter shock." It's basically under cover from October to May. I have always kept on top of water balance for the past 4 years or so that I have had the pool and never had any type of problem with alge, nitrates etc. that I knew of.

Could there be something that I'm doing or not doing to cause it to be badly neglected?

I understand that the advise that is being given out here is purely based on my descriptions and your experience, and that without knowing every factor involved it's at times a best guess. I do appreciate it.

Over the past 2-3 weeks I have put in approximately 75-100 gallons of chorine 3-4 gallons at a shot. As long as there is no fear of damaging (with proper testing) the pool or liner, I'll go back to that approach and see where I get.

Sean

 

[klavant]

Any new newsonthis situation? I've got the exact same scenario. I've resorted to the bucket test suggested by Jason.

 

[SeanH]

Any new newsonthis situation? I've got the exact same scenario. I've resorted to the bucket test suggested by Jason.

I never got around to the bucket test. I'd be interested to see how you make out with it.

I'm at the point now where I test the water at night and add enough chlorine to get it up to 3-5ppm.

I seem to lose 1-2ppm overnight, but who knows.....maybe i've underestimated the volume of my pool.

Maybe the next time I shock it I'll stock up on 50 gallons of chlorine and see if I can get my overnight loss down, but I'm not overly concerned with it at this point. I still need to bring my CYA up a little so that could be part of it as well.

I can say that I'm gratefull to have found this site before investing in the equivalant amount of shock at my local pool store to clear the alge that I had. I would have spent a fortune given the amount of chlorine I had to put in.

Sean