Chlorine level

[65corvette]

I've been writing in regarding not being able to keep my chlorine levels up. I decided to shock my pool which I did on 5-15 8:30pm.
Levels since: 5-16 1:30pm FC=13 5-16 7:45pm FC=13 5-17 11:45am FC=10 5-18 (today) 2:30pm FC=5
I did have swimmers yesterday for the first time-that may make a difference. But should the level drop from 13 to 5 in 2 days? All my other level seem to be stable.

 

[257WbyMag]

Well, it can drop like that. It just depends on things like the amount of sun your pool gets, what your CYA level is, bather load, and what organics are currently residing in your pool water. Go ahead and give us a full set of test results so that we can see the big picture.

 

[chem geek]

See this thread. Any kids in the pool?

It's interesting that on 5/16 you didn't seem to lose any chlorine -- I wonder if it was cloudy. You had a drop from 10 to 5 in about 27 hours and that's on the high side, but as was noted it depends on the CYA level and bather load. How many people were in the pool? If you didn't have any bather load, then with a CYA of 80 ppm I'd expect a drop more like 20-25%, so from roughly 13 to 10, for example, which you had when there weren't bathers.

If you consistently notice the FC holding overnight but dropping during the day a lot even without swimmers, then I'm not sure what's going on since your CYA is at 80 ppm and you've got 50 ppm borates in the pool as you described in this post.

Richard

 

[65corvette]

As requested, complete results: FC=5 CC=0 TC=5 TA=80 pH=7.8 CYA=80 5-19 @ 11:45am
FC was 5 yesterday, I added 60oz. bleach last night and level is still 5 today. I added 60oz more and will recheck.
I had 2 people in the pool and they were both adults (so hopefully it's a safe assumption that no one peed in the pool!)
The presence of organics in the water has been continually brought up. Could I get more information on that topic?
I don't know why I'm having problems - things have been trouble free since I found your site in September. At this rate, I will be keeping the bleach manufacturers in business, so a solution would be great! Thanks! :-D

 

[frustratedpoolmom]

2 things consume chlorine. Organics and sunlight. Best way to figure out what's happening is the overnight test.

You test the FC, after sunset , 30 minutes after the last bleach addition, and record the result. In the morning before the sun hits the pool, (make sure the water has been circulating for 1 hour or more) retest the FC. Compare the two results. IF you lose more than 1ppm then something organic is consuming the chlorine and you need to shock.

 

[65corvette]

I shocked on 5-15 - would that not have taken care of any organics that may have been in the water?

 

[lovingHDTV]

You have to keep the FC level at shock level until there is less than a .5 drop in FC overnight and less than .5 CC. At that point you should no longer have organics in the pool.

However, do you have a source of organics that could be getting added to your pool later? I know that I have trees that continually drop organic matter into my pool. I therefore have a much higher chlorine consumption than others.

 

[65corvette]

I guess that I am going to have to do the overnight test (not thrilled about getting up at the crack of dawn though!). And yes, I do have 1 pain of a tree that drops lots of dead blossoms in the pool, but it has always been there. So, I wouldn't think that would be the issue.
Do I understand correctly that if I do the overnight test and the FC drops more than 1ppm, then I have organics and I have to shock until the FC holds overnight? :|

 

[Butterfly]

......
Do I understand correctly that if I do the overnight test and the FC drops more than 1ppm, then I have organics and I have to shock until the FC holds overnight? :|

Yep.

 

[duraleigh]

I guess that I am going to have to do the overnight test (not thrilled about getting up at the crack of dawn though!).

You don't have to. You simply have to get up before the sun (UV rays) have the opportunity to start killing some of your chlorine. 45 minutes after sunrise is fine as long as the direct sun is not on the pool.