First swim after changing over to BBB...questions

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contento

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May 28, 2008
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My FC held strong at right around 5 overnght, so, the pool is open for business. The family went swimming today for the first time since starting this last week. I came home to jump in myself and decided to test the water...because I can with my new test kit :wink:

FC=1 ?! 1ish even

What in the world would cause a crash that fast? Hot Florida day + few swimmers for a couple of hours = 4 point drop in FC?

Not only that, but my CYA which was high at 70-75 SHOT up to like 100. :x Would THAT cause the FC to crash? Makes sense. SO the question is then what would cause the CYA to skyrocket after a few days steady around 70?

Needless to say, the drains are open and I'm dropping some water to replace tonight. The question is, how much should I be replacing (not that I can meter the amount I'm changing more than a physicall drop measurement at pool level...like drop the pool 3") (16x30 rectangular diamondbrite finish inground).

Thanks again all!
 
Testing error on the CYA...nothing else makes sense.

Have you tested for CC's in the pool? EDIT: from your previous posts, it appears you cannot. The FAS/DPD test for chlorine is really the only test accurate enough to test for overnite stability of FC.

I suspect your FC loss is the result of remaining organics in your pool and you'll need to keep the FC quite high until they are gone or, probably better, bring your pool up to about 25-30ppm to shock it and then let it drift back down to normal. (5-8ppm)
 
If you get ancy waiting for an intelligent response, you could always retest... just to make SURE you did everything right, and you're not wasting water, etc just because... know what I mean?

No expert here, but your readings do seem odd... but not enough for you not to be swimming... RIGHT NOW!!!!

EDIT: Obviously Duraleigh was typing slightly faster than I was, at similar times... HIS answer is the Intelligent one (even my rookie guess kinda agrees with his.)


Good luck,
Steve
 
if you don't have a SWG, might as well drop the CYA level some by draining and refilling, 50 might be easier to manage.

algae can skew results, so perhaps you have some growing in there. a 2 ppm drop is regular, and I don't doubt that maybe another 1ppm drop from a swimmer load.

with CYA of 70, you should've maintained a min FC of 5ppm and a target of 8ppm. and as duraleigh said, you will need 25-30ppm to shock.

http://www.troublefreepool.com/viewtopic.php?t=2346
 
Thanks all. I dropped the CYA to 50 with some water change. If the FC is stable overnight with the pump running, then why would the drop be contributable to organics in the pool?

I'll know more later after another sunny day and kids swimming.
 
If free chlorine remains the same overnight with a FAS-DPD chlorine test then there isn't anything growing in the water.

I suspect that between the sunlight and the people you just used more chlorine than you expected.
 
I still don't have the FAS DPD test, but the color result is essnentially the same night to morning. I just got home and tested the FC after a long day of swimming (kids) and a hot sunny day: FC=1ish again. Is it safe to say that I'm going to lose 4 points per day when we swim? That calculates to over a full gallon of chlorine per day to maintain a 5 (which actually is a little lower than the recommended 5.7 or so that I've read). Obviously chemistry is chemistry but that seems excessive (from the guy who was told by the pool store to just dump in 1 2.5 gallon jug of their TriChlor each week to shock...and has had problems for 11 years :roll: )

So, with that said...is it unusual in my situation to consume more than a full gallon of household Chlorine Bleach per day?

The pool looks amazing..BEST ever by far. EVERYTHING tests perfect right now:

FC=~5
pH=7.5
TA=110
CH=225 *
CYA=50

* CH (this probably could go up a bit in a diamondbrite finish pool right?) I took this sample deep too as I was told thats the only way to get an accurate reading as it's a heavier compound.
 
Without the FAS-DPD chlorine test there is no telling what your FC numbers really are or if there is anything growing in the water or not. All of the other tests are significantly less precise except at very low FC levels. Testing errors on the CYA test are also quite possible. A lower CYA number could easily give the results you are seeing.
 

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You cannot make cyanuric acid in your pool. If you don't add it, and you don't add stabilized chlorine like dichlor/trichlor (which contains CYA), your cyanuric acid levels cannot go up. I think it's a testing error. The other possibility though is that you dumped a lot of CYA into your pool, and it moved to the filtration system or sat in the skimmers and took a few days to dissolve. My CYA levels will continue to climb for several days after I add it to the skimmer, and the DE filter pressure will increase during this time.

Chlorine demand is hard to pin down. Bather load, sun, nascent algae/bacterial blooms you cannot see, or other factors can all contribute to increased chlorine demand. This is why we test daily. I sometimes see my pool's demand spike up or down and have to compensate for it. If it shoots down, I add bleach to bring it up fast, if it goes up, I just turn off the SWG and wait. If your pool continues to consume massive amounts of chlorine, then keep investigating, but if it's occasional, you'll probably never figure out why, and it's not necessarily a problem as long as you are vigilant and maintain your chlorine levels.

Good testing kits are also important. Buy a Taylor K-2006 or an equivalent drop-based kit with a FAS-DPD test if you don't have one already.
 
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