CYA dropped significantly.

Sunnier

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Aug 13, 2021
6
Arizona
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10000
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Liquid Chlorine
I have being using this website and trying to learn more about taking care of our pool for a while now. This is my first post though.
The pool was not in a good shape this whole summer season, and I am trying to fix it before the season is over. So, here is the problem I am having. I started the SLAM process three weeks ago. The CYA was below 20 because of rain, so I added 4lb of the Clorox stabilizer and got cya up to 30. PH was around 7.8. After 5 days of adding the stabilizer, I started the SLAM. It was going well. All the visible green algae was gone, and I was left with a blue but very cloudy pool. I kept up the shocking level, and day by day the pool was clearing. Several days ago we had some rain, and two days later I noticed that the chlorine level was going down quicker than usual. So, I tested the cya level today, and it was below 20. The dot didn't despair even though the test tube was full. So I assume it's below 20. My question is does rain make the cya go down this low? Also, is it normal for the chlorine to be consumed this quick if the cya is low. And how can I raise the cya up with out interrupting the SLAM process.
 

Texas Splash

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Welcome to TFP! :wave: No, rain by itself doesn't lower CYA, but if you got enough rain to where you had to let water out, then that could. Keep in mind there is about a 10-15ppm variance in the CYA testing. It's still hot across the states, so with a low CYA the FC will certainly disappear rather quickly, especially if it is taking care of algae. You can increase the CYA at any time.
 

Texas Splash

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Just in case you need it ....

Adding CYA:
To increase CYA via granular stabilizer, place the required amount as calculated by the Poolmath calculator into a white sock and place in the poolside skimmer basket. For those concerned about suction flow to the pump, suspending the sock near a return jet or from a floating device will also suffice. Best never to allow undissolved granules to rest directly against the pool surface. Squeeze the sock periodically to help it dissipate. Once dissolved, consider your CYA adjusted to that programmed (target) level. CYA test readings should show a rise in 24-48 hours, however some pools may experience a longer delay to fully register. Best to confirm final CYA in about 5-7 days before adding any more stabilizer/conditioner.
 

TexEdmond

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Jun 16, 2021
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Edmond, OK
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Welcome to the forums! You're in the right place for help. I'd imagine just about anywhere in Arizona you're getting loads of UV light from the sun on your pool. I'm not aware of anything that will neutralize FC faster than: UV light, algae, and pee.

You're probably well served to bring your CYA levels up significantly higher to remove the sunlight from the equation. You know how to SLAM, so the algae should be gone soon enough. The third? weelllll....

If you've been SLAMming already, you might consider a quick rinse of your filters, then adding some CYA and letting it circulate for a day or two. Keeping your pH closer to 7.2 before doing the SLAM will also help the chlorine to sanitize better.

FC/CYA Chart

Good luck, and you've got this thing!
 

Sunnier

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Aug 13, 2021
6
Arizona
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10000
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Thank you for the replies. I will start with rasing up the CYA level and then restart the SLAM again.
 

TexEdmond

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Jun 16, 2021
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Edmond, OK
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Thank you for the replies. I will start with rasing up the CYA level and then restart the SLAM again.
I shouldn't have used the word "significantly." CYA is easy to raise and a lot of work to lower. Shoot for 40ppm and if you're still noticing a large daily loss after your SLAM is finished, you might consider heading to 50.
 

Sunnier

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Aug 13, 2021
6
Arizona
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10000
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Is it better to use the CYA powder or should I use the shock bags (Sam's Club brand) since it does raise the CYA too. I still have some left from last summer. That way I don't interrupt the SLAM process while trying to raise the CYA.
 

JimMarshall

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Jun 5, 2017
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Oil City PA
Is it better to use the CYA powder or should I use the shock bags (Sam's Club brand) since it does raise the CYA too. I still have some left from last summer. That way I don't interrupt the SLAM process while trying to raise the CYA.
If you have trichlor or dichlor shock you can certainly use them to increase your FC while increasing CYA as well.

However either way there is no need to interrupt the slam. Add CYA using the sock method while continuing to SLAM as usual
 

Mdragger88

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Jun 1, 2018
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Those will affect your ph - if they are dichlor or trichlor.
Adding dry stabilizer in a sock won’t affect your slam. As soon as the stabilizer in the sock is dissolving assume its in the water & adjust your fc slam level accordingly per the FC/CYA Chart
 

TexEdmond

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Jun 16, 2021
511
Edmond, OK
Pool Size
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You'll just need to add more FC to maintain SLAM levels. Your choice.

I "used up" old chemical (mostly Cal-Hypo) when I changed over to TFP just because I didn't know how to get rid of it. I wish I hadn't... my pool water didn't go TFP clear until I was finished yanking on the CH and TA numbers by adding chemical that wasn't doing what I wanted. When I worked my way into the bucket of trichlor powder shock, I just gave it away on the neighborhood FB page. Granulated CYA is pretty cheap and keeps forever as long as it's dry. That's what I have now, and my chemicals shelf is very simple.
 
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TexEdmond

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Jun 16, 2021
511
Edmond, OK
Pool Size
25500
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
the dry stabilizer will effect his pH as well
Not nearly as much as trichlor.

In order to increase CYA 10ppm in a 10k gallon pool:

Trichlor - add 1.5lbs
Raise FC by 16.0
Raise CYA by 10.0
Lower pH by 0.9

Dichlor - add 1.7 lbs
Raise FC by 11.0
Raise CYA by 10.0
Lower pH by 0.4

Dry Stabilizer - add 0.85 lbs
Raise CYA by 10.0
Lower pH by 0.2
 

JimMarshall

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TFP Guide
Jun 5, 2017
1,090
Oil City PA
Not nearly as much as trichlor.

In order to increase CYA 10ppm in a 10k gallon pool:

Trichlor - add 1.5lbs
Raise FC by 16.0
Raise CYA by 10.0
Lower pH by 0.9

Dichlor - add 1.7 lbs
Raise FC by 11.0
Raise CYA by 10.0
Lower pH by 0.4

Dry Stabilizer - add 0.85 lbs
Raise CYA by 10.0
Lower pH by 0.2

This is absolutely true, I just didnt want someone to read this and assume that adding CYA has no effect on other levels.
 

Sunnier

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Aug 13, 2021
6
Arizona
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10000
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Yesterday, I added dry cya to the pool using the sock method, and I am keeping up the slam level recommended for a cya of 45. 45 is what I am aiming for for the cya level. I used the pool math calculator to figure out the measurements. My question is how long should I wait before checking cya level?
 

Mdragger88

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24 hrs should be good- if the test shows above 40 you count it as 50 ppm & chlorinate accordingly. No in betweens - always round up to the next 10. 👍🏻
 
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TexEdmond

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My question is how long should I wait before checking cya level?
Recommendation is to verify CYA at least 24 hours after adding so it has plenty of time to mix and dissolve thru the filter. My experience was I added it very slowly, ~12oz at a time over 2 days, then checked 2 days later because I didn't want to go past the number.
 

Sunnier

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Aug 13, 2021
6
Arizona
Pool Size
10000
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Chlorine
Liquid Chlorine
Today I did all the chemical tests to check the condition of the pool water. I did this test around 8 am. Yesterday, I added bleach as recommended by the cya/ chlorine chart around 7pm. Here are the readings:
FC 1.5
CC 1
PH 7.2
CH 850
TA 80
CYA 60
Do I keep the slam or should I address the CH high level first?
 

mknauss

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You are reaching the level of CH that becomes difficult to manage.
I would suggest you plan on a complete drain and refill here in the next several weeks.
Do you have a whole house water softener? After a water exchange, it would be wise to use softened water for make up water.

Your FC is way too low for the CYA level.
 

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