CYA and latitude

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M

mjc123

Well-known member
Jul 20, 2018
114
Halifax, NS (Canada)
Pool Size
18500
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
I see the recommended CYA level for a SWG pool is 70-80, but it begs the question if latitude should matter. For example, given two otherwise identical pools- one in northern Minnesota (49 deg) and one in Key West (24.5 deg)- does it make sense that they target the same CYA level?

I guess the basis of my question is whether I, at latitude 44.7 deg, really need 70-80 ppm CYA. I’m currently at 40 as of last night’s test
 
You can get away with CYA 40. You have a large cell on a medium size pool. If you went to CYA 60 you would reduce your cell run time a bit and extend the life of your cell.

Any reason you don’t want to bring your CYA to 60?
 
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Nope, none at all. Just curious if the 70-80 recommendation is good regardless of how far north one is. My understanding is the optimal CYA level attempts to balance FC loss to UV against maintaining higher FC levels (greater cost of chems). Assuming that understanding is correct, then wouldn’t the optimal level decrease as UV intensity decreases? If the answer is no, then I’m totally happy bringing the pool up to 70-80. I only ask because I don’t know and thought it was worth the ask, given that lowering CYA later is a pain
 
Your theory is correct. The more sun the more CYA helps to reduce chlorine loss. So, in Canada vs Texas there would be less chlorine loss in Canada for the same CYA. Canada would lose less FC to UV at CYA 60 than Texas would. But, it is also true that any pool will lose less FC with more CYA. So, your pool will lose less FC with CYA at 80 than it will with CYA at 60.
 
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