CYA dropped 40 in a week

Tsteiny

Member
Aug 29, 2022
21
Mesa, AZ
Pool Size
9600
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool SJ-20
So I’m in the middle of a slam. CYA levels where 50-55 for a solid week. Was mainting FC levels for the correct CYA levels. I had to go out of town for a week. During that week, my wife did an awesome job testing the pool in the morning and at night and was adding the proper amount of chlorine. I had to order new CYA solution as I ran out. Tested it tonight at it’s around 10ish. I understand that cya loss can be elevated a little during a slam. But I don’t have any leaks. We had zero rain the entire time I was gone. I’m at a loss. The solution is good till 8/24. Why am I loosing so much CYA? I’m now 2 full weeks into the slam as well
 

Mdragger88

Bronze Supporter
TFP Guide
Jun 1, 2018
6,952
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
Hot water also plays a role in cya degradation, it’s probably been fairly warm in AZ. Even so, That is quite a drop in cya level. Did you do the test outdoors in bright light on a sunny day? Have replaced any water due to frequent filter backwashing during slam? (Your filter type isn’t listed in your signature)
 

amin36

In The Industry
Nov 24, 2017
154
shahsavar
This might be because of free chlorine getting to zero.when this happens some bacteria turn CYA into ammonia and as a result your CYA amount partially or entirely lowers.maybe she has forgotten to add chlorine at some point.this is what usually happens when you manually add chlorine to pool water!
 
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duraleigh

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Sebring, Florida
I suspect testing error somewhere. Ammonia producing bacteria is not applicable in this instance (AND RARELY IS). Warm weather can't account for that loss, either.

Why don't you start over? Post a current set of test results and restart the SLAM based on those.

During the SLAM you should ignore CYA testing.....it is not part of the process which must be followed precisely.
 
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Tsteiny

Member
Aug 29, 2022
21
Mesa, AZ
Pool Size
9600
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool SJ-20
This might be because of free chlorine getting to zero.when this happens some bacteria turn CYA into ammonia and as a result your CYA amount partially or entirely lowers.maybe she has forgotten to add chlorine at some point.this is what usually happens when you manually add chlorine to pool water!
that I know didn’t happpen. Watched wife test twice a day on FaceTime and never dropped below 17.
 
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Tsteiny

Member
Aug 29, 2022
21
Mesa, AZ
Pool Size
9600
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool SJ-20
I suspect testing error somewhere. Ammonia producing bacteria is not applicable in this instance (AND RARELY IS). Warm weather can't account for that loss, either.

Why don't you start over? Post a current set of test results and restart the SLAM based on those.

During the SLAM you should ignore CYA testing.....it is not part of the process which must be followed precisely.
So I tested the cya for two days prior to the slam and it was 50-55. I did test the cya again this morning at it’s more like 20ish. The tube is almost full before the dot goes away. So apologies for thinking it was 10. I do have the 50ppm cya test and when tried this morning in the same light condition, it was right on 50. So the regant isn’t it.

My fc loss last night was 1.5ppm so I’m so close to finishing the slam. CC was zero. Is it okay to leave cya at that level for now and bring it up after slam? Is it okay to add a little conditioner now? Or do you still recommend starting the slam over again?
 

duraleigh

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Sebring, Florida
Yes. A CYA level of 20 will allow you to finish the SLAM. Use 10 ppm FC as your SLAM Value

Probably a better choice would be to add 10 ppm CYA (conditioner) to your pool and assume you have a total of 30 ppm CYA.

Then use 12 ppm as your SLAM value. Keep your FC up around 12 ppm until you finish the SLAM.......you sound close.
 
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