Acceptable CYA Level in a Pool in Direct Sunlight

axfx

Member
Jun 22, 2021
6
DC
The CYA for our pool is currently 90. Our pool is in 14 hours of direct sunlight a day. Is this too much CYA or the appropriate amount? I have found sources online that state if your pool is in direct sunlight, you should maintain CYA levels of 80-100.
 

Texas Splash

Mod Squad
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Jun 22, 2014
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Texas, San Antonio/Marion, South-Central Area
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Welcome to TFP! :wave: Here at TFP, we first split CYA recommendations between salt and non-salt pools. Salt pool we recommend a CYA of 70-80, while non-salt somewhere in the 30-50 range, perhaps higher in very intense regions. The amount of sunlight and intensity of the sun UV (i.e. AZ versus MD for example) come into play. See our FC/CYA Chart and the link below for more details.

 

zea3

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Jul 10, 2009
14,313
Houston, Texas
Hi, welcome to TFP! I would say 80 to 100 is too much for any pool. There is a fine line between protecting chlorine and rendering it ineffective. It is important to maintain the correct ratio of chlorine to CYA, and most pool care sites will not tell you this. If your CYA is 90 but you are having a hard time keeping the pool clear, then you don't have enough chlorine to balance the CYA. Anything over 100ppm of CYA and it becomes too impractical to keep FC in ratio to CYA.
 

axfx

Member
Jun 22, 2021
6
DC
Welcome to TFP! :wave: Here at TFP, we first split CYA recommendations between salt and non-salt pools. Salt pool we recommend a CYA of 70-80, while non-salt somewhere in the 30-50 range, perhaps higher in very intense regions. The amount of sunlight and intensity of the sun UV (i.e. AZ versus MD for example) come into play. See our FC/CYA Chart and the link below for more details.


We have a non-salt pool, we also do not have a SWCG. The UV index for Maryland is about 7.5-8.5. As a comparison point, the midwestern states and Texas are usually about 10-12. Arizona, which you referenced in your post, is about 11-13.

With this knowledge, do you think a CYA level of 90 is too high? What would you aim for as an estimate, given the UV index in Maryland?

Also, when you say perhaps higher for more intense regions, how much higher would you recommend? I am not in Arizona but I am curious at this point regarding CYA levels for somewhere with intense sunlight such as Arizona.
 

Katodude

Silver Supporter
Aug 22, 2017
2,057
West Palm Beach/Florida
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For a non salt pool in Maryland that is probably high. I would keep my FC at the high range of scale and you should be ok. Are you dosing with LC daily, how often do you test. Do you have a good test kit? Good news is your pool should be getting pretty hot and it summer so you will get lots of rain. Between the two of those you should see you CYA lower by itself.

non scientific but I find that when the pool reaches about 88 degrees the CYA starts degrading faster (it has something to do with the flux capacitor).
 

PoolGate

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TFP Guide
Jun 7, 2017
7,258
Damascus, MD
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I'm in MD and I'm at 70 with a saltwater pool. You can go with 90 but keep in mind you'll need to go with a higher chlorine level like a 9.
 

axfx

Member
Jun 22, 2021
6
DC
For a non salt pool in Maryland that is probably high. I would keep my FC at the high range of scale and you should be ok. Are you dosing with LC daily, how often do you test. Do you have a good test kit? Good news is your pool should be getting pretty hot and it summer so you will get lots of rain. Between the two of those you should see you CYA lower by itself.

non scientific but I find that when the pool reaches about 88 degrees the CYA starts degrading faster (it has something to do with the flux capacitor).

I just ordered the TF-100. Going to take pool management much more seriously.

My FC is about 4 w/ a CYA of 90. I was previously using tablets.
 

mguzzy

Gold Supporter
With this knowledge, do you think a CYA level of 90 is too high? What would you aim for as an estimate, given the UV index in Maryland?
The short answer is 90 is too high. But lets backup... how are you getting 90? Are you testing yourself or using the pool store? If you are using a Taylor based test and doing your own testing then we have more confidence in your value. I like Kato's suggestion.. you can probably bring it down on its own from rain dilution if this summer is typical other summers I have experienced in DC. But if you are chlorinating with stabilized tabs.. you will be fighting an up hill battle. You will need to switch to liquid chlorine.
 

clambert1273

Gold Supporter
Jun 13, 2013
1,110
Gilbert, AZ
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We have a non-salt pool, we also do not have a SWCG. The UV index for Maryland is about 7.5-8.5. As a comparison point, the midwestern states and Texas are usually about 10-12. Arizona, which you referenced in your post, is about 11-13.

With this knowledge, do you think a CYA level of 90 is too high? What would you aim for as an estimate, given the UV index in Maryland?

Also, when you say perhaps higher for more intense regions, how much higher would you recommend? I am not in Arizona but I am curious at this point regarding CYA levels for somewhere with intense sunlight such as Arizona.
I am in AZ and run 60cya while using liquid chlorine for my swg I will up it to 70-80 range, it is very brutal here Your area doesn't need these levels
 

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Katodude

Silver Supporter
Aug 22, 2017
2,057
West Palm Beach/Florida
Pool Size
15000
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Plaster
Chlorine
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SWG Type
Hayward Aqua Rite (T-15)
I just ordered the TF-100. Going to take pool management much more seriously.

My FC is about 4 w/ a CYA of 90. I was previously using tablets.

Good job on the kit. Bad job on the FC. Add LC to that pool right now!!!
I am in Florida and my CYA is currently 90 (down from 100 when I added too much CYA). I have a SWG but still keep my FC around 12. That number sounds high and scary but its not. Pool is crystal clear, and does not smell like chlorine. Stay on the high side of the FC/CYA chart and you will live through it.

Drop to low, then you get algae and then life sucks. Cant SLAM at a CYA of 90.
 
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