My CYA seems to be disappearing

ajones02

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Feb 4, 2010
118
Keller, Texas
i need to chime in on this as well and looking for some assistance. on a previous post of mine, i mentioned that my CYA seems to be disappearing. i am adding about an inch of water every 3 days or so due to evaporation but with everything i've read, that should not be enough to cause the sudden drop in CYA. i read above that it's possible to be broken down into amonia and that a shock is necessary. just a few quick notes on my pool so far this summer. the lowest the FC has been was 3.5 and the highest CC reading I've had was 0.5 so I've never shocked my pool so to speak. the water has look good but at times not polished...Based on Jason's feedback above, is it advised that I go ahead and shock my pool to the proper levels to see if the CYA continues to disappear?

Two weeks ago my CYA level was 80 and then i tested it last night and it was in the 55-60 range. same thing happened about a month or so ago as well. i also added 2 lbs of stabilizer this morning before coming to work.

Thanks for any assistance.
 

Melt In The Sun

TFP Expert
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Oct 29, 2009
3,899
Tucson, AZ
Re: CYA level dropped off the charts.

ajones, CYA -> ammonia can't happen in a sanitized pool. Evaporation and refill will have no effect on your CYA level, since the CYA doesn't evaporate with the water. I don't know what's happening...
 

ajones02

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Feb 4, 2010
118
Keller, Texas
Re: CYA level dropped off the charts.

thanks melt in the sun for the quick response. just been a frustrating process. maybe i need to take a water sample to the pool store to verify the CYA as well.
 

bk406

Well-known member
Dec 3, 2009
2,690
Central Massachusetts
Re: CYA level dropped off the charts.

ajones,

Does your salt level go up at all when you lose the inch of water, or at least stay stable after you add water? Losing CYA like that and adding an inch of water every 3 days could be a leak. If the salt is dropping too, that could confirm. If the salt is stable, not sure what to make of it. Have you tested for ammonia?
 

ajones02

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Feb 4, 2010
118
Keller, Texas
Re: CYA level dropped off the charts.

actually FPM suggested a leak somewhere but the salt has remained stable at approx 3800 ppm for the past couple of months. i have not tested for ammonia yet. i was just actually reading some additional post and it appears that maybe my pool isn't quite as sanitary as i think it is and may need to test for ammonia. would the recommendation be test strips or take a sample to the pool store? if i do have ammonia, what is the process for removing that?
 

bk406

Well-known member
Dec 3, 2009
2,690
Central Massachusetts
Re: CYA level dropped off the charts.

go to a pet store and pick up a kit. Not sure a pool store would test for it. they are pretty cheap. Chlorine and lots of it is the fix if you have it. My guess is you dont.
 

ajones02

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Feb 4, 2010
118
Keller, Texas
Re: CYA level dropped off the charts.

ok, i'll do that this afternoon and let everyone know the outcome.

since this is my first inground pool, is an inch of water every 3 days or so a lot to replace? it's been around 100 degrees here now for about a week and a half
 

ajones02

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Feb 4, 2010
118
Keller, Texas
Re: CYA level dropped off the charts.

one other question in regards to a sanitized pool, i do have crepe myrtles somewhat close to the pool and have had a ton of the blooms fall into the pool over the past couple of weeks, would this possibly help the situation along?
 

Melt In The Sun

TFP Expert
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Oct 29, 2009
3,899
Tucson, AZ
Re: CYA level dropped off the charts.

I don't think that's a lot; it sounds reasonable given the hot days. You can do a bucket test to be sure; fill a bucket partially with water and see you lose water from it at the same rate as from the pool. If you have a leak, the water level in your pool will fall faster than in the bucket.
 

ajones02

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Feb 4, 2010
118
Keller, Texas
Re: CYA level dropped off the charts.

first of all let me apologize to DLO for kidnapping his thread. if i need to start a different one i'd be happy to.
Moved into it's own topic. JasonLion

with that said, i stopped by and bought an amonia test at walmart and completed a full set of test and here are the results

FC 5.0
CC .5
TC 5.5
PH 7.2 was 8.2 on my original test but added acid to bring this down.
TA 100 was 140 on my original test but dropped after bringing the PH down
CH 300
CYA 55 added 2 lbs yesterday to bring to 75
SALT 3800 PPM
WATER TEMP 90 (was 86 this morning)
Ammonia best i can tell it was between .50 and 3.0 based on the colors. my best guess would be closer to 1.0 or 1.5 but there was noway to verify that.

Thoughts?
 

chem geek

TFP Expert
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Mar 28, 2007
12,083
San Rafael, CA USA
When there is chlorine present in the water (i.e. a positive measurable FC reading), then there won't be any actual ammonia and the ammonia test kit will instead be measuring the amount of monochloramine in the water (chlorine and ammonia combine very quickly to form monochloramine). An ammonia test reading (with FC in the water) of 0.5 ppm would show up as 2.5 ppm CC since the units of measurement are different so something is very inconsistent here. It's certainly possible to have CC higher than predicted by the ammonia test (i.e. a CC higher than 5 times the ammonia test level), but the other way around doesn't make sense. If your CC were 5 ppm and your ammonia test around 1 ppm, then that would be consistent.

I'd just chalk up the CYA drop to some sort of strange mystery and just adjust the chemicals and move on from here.