Question about FC/CYA recommendations in salt pool

[Dennyhle]

I've been using this chart: Chlorine / CYA Chart

I didn't notice that there was a separate tab for chlorine vs salt. I have a salt pool. I understand that a higher CYA makes FC less effective but why is the FC recommendation for a given CYA level for a salt pool lower than liquid chlorine? At 70 CYA, TFP recommends FC of 5 for SWG but 8-10 for liquid chlorine? Why is this?

I have an oversized salt generator for my pool and I am able to maintain my FC 7 with CYA of 45ish. Is it really necessary to bump the CYA up to recommended 70?

 

[Texas Splash]

Many threads about this subject on the forum. Rather than re-invent the wheel, below is one such discussion that should explain the FC-CYA relationship as it applies to salt pools. Give it a read. If you still have questions, let us know and we can address those concerns.

CYA in salt vs non-salt pools

I see recommendations of 30-50 ppm CYA for regular chlorine pools and 70-80 for salt chlorine pools. Given that CYA "protects" the chlorine from UV and at the same time reduces the effectiveness of chlorine, why the different levels for salt vs non salt pools? I've searched the CDC website...

www.troublefreepool.com

 

[Steve-D]

As a new plaster/SWG pool owner I've asked this question myself and as it was explained to me the long term goal is to save money by extending the life of the SWG so you don't have to replace it as soon as you might have to if running it at closer to its capacity.

This is accomplished by the higher CYA to keep more FC in reserve so you can aim for a lower FC target. The "reserve" mitigates the risk of having FC drop into a danger zone even while aiming for that moderately low FC level. Once you get to the target FC it should take less effort from the SWG to keep it there which means you can run the SWG at a lower % of its capacity and doing that extends the useful life of the SWG.

[edit] Here is a link to the thread with my question.
[edit2] and this explanation from @Texas Splash :
see: FC/CYA for swg

Basically, with SWGs you have a lower FC level being produced & maintained continuously through the 24 hr period as opposed to the one-time liquid dumping. That along with the production of chlorine gas (versus liquid) has shown that a higher CYA protects the chlorine gas better and helps to maintain a more consistent/reliable FC level. The generic 30-50 recommended range is still provided by many in the industry and assumes pool owners will use chlorine tabs that are not only very acidic, but also use stabilizer in each puck. There fore that level increases exponentially requiring the pool to be drained in a short period of time. Today, there are more manufactures of pool products (i.e. Circupool) who recognize the need for a tailored FC-CYA relationship as noted on the FC/CYA Chart, that how recommend a CYA of 70-80 for those very same reasons.

 

[SoDel]

I think the FC recommendations are reasonable minimums and there is room for reasonable upward departure. I run my FC at 12% CYA for the floor, and often due to cloudy days and so on, it is well above that. Based on “rough estimate” 10k hr run life, my salt cell should last about 10 yrs. It won’t, but cell life from using it isn’t my primary concern. It will die of something else before then. You maybe need to balance the economics of how much you run it with how much you want to fuss with it and how your pool sort of reacts to the levels. I got too much going on to deal with algae so a prudent margin (HOCL always above 0.05 ppm with the typical salt cell pool 7.8+ pH) is where I settled.