Why is CYA target different for swg and manually dosed pools?

[jalapenopopper]

There are a number of old threads on this but not clear answers.

If the higher CYA help a swg by working less, wouldn’t the same level allow one to use less liquid chlorine for the same reason of protecting it from the sun?

also, are there any documented experiments of maintaining water samples with varying CYA and FC levels and recording the algae growth? Everything I have read if casual and anecdotal.

 

[mknauss]

If one adds 0.3 ppm FC worth of liquid chlorine each hour, or whatever is your required addition, it does equate. But most add liquid chlorine once per day. Even liquid chlorine pumps add most of the chlorine in an hour or so each day.

The elevated CYA for SWCG pools was based on anecdotal observations by early and current TFPC members. I am one of them. If my CYA drops below 70 in the summer, my FC use rises by 25-50%.

If you wish to operate at a lower CYA, do it. Just be sure the FC does not drop below minimum anytime during the day.

 

[jalapenopopper]

My pool is liquid chlorine with 45 ppm CYA. I manually add liquid chlorine and am considering if I increased my CYA to 70 that I may lose less chlorine to the UV degradation. Are there drawbacks to increasing the CYA to the SWG levels? I understand the FC would need to increase, but I wonder if overall chlorine use may go down.

thanks for your feedback. I do not want to increase CYA without hearing from the forum since I do not wish to have to drain and replace water down the road.

I may set up some bucket chemistry experiment with some algae water and differing CYA levels to satisfy my curiosity.

 

[mknauss]

If manually adding chlorine maintain your CYA at levels shown in Recommended Levels.

You might go to 60 ppm CYA, but I would not go above that. Degradation of the CYA and overflow from rain should lower your CYA back down to 40 ppm or so by winter.

 

[Newdude]

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[jalapenopopper]

If manually adding chlorine maintain your CYA at levels shown in Recommended Levels.

You might go to 60 ppm CYA, but I would not go above that. Degradation of the CYA and overflow from rain should lower your CYA back down to 40 ppm or so by winter.

I am curious why 70 ppm CYA wouldn’t give me the same benefit of shielding the chlorine from UV light as is recommended with a SWG. I have seen the chart, I don’t understand why the CYA targets are different.
Thanks

 

[mknauss]

It might. Try it. Only down side is if you have to SLAM. If you never, and I mean never, go below minimum FC you will be fine.

 

[jalapenopopper]

There does not seem to be a good reason for the recommended CYA levels to be under 50 ppm and different for SWG, which I find surprising since these guidelines are shared ubiquitously.

 

[Newdude]

There does not seem to be a good reason for the recommended CYA levels to be under 50 ppm and different for SWG

There is a great reason. Adding liquid is an instant spike, and it takes 24 hours to drift down. The burn off matters a lot less.

The SWG produces so slowly that it needs enough buffering to retain what it produces. And over 24 hours it hits the same target when dialed in.

When a problem arises the salt pools need a lot more chlorine to fight it, so that’s heavily weighed into the factoring as well. Why go high CYA with LC if you don’t need to (for most) ?

 

[jalapenopopper]

The burn off seems to be requiring more chlorine than an elevated CYA and chlorine levels.
Thanks for the reply. I’m interested to see if I could use less chlorine over time with higher CYA and LC dosing, but am cautious considering how CYA increase cannot be undone easily or efficiently.
Does anyone run a liquid chlorine pool at 70-80 CYA and have experiences they can share?
Thanks

 

[Newdude]

I’m interested to see if I could use less chlorine over time with higher CYA and LC dosing, but am cautious considering how CYA increase cannot be undone easily or efficiently

And therein lies the quandary…….

Does anyone run a liquid chlorine pool at 70-80 CYA and have experiences they can share?

I don’t recall any, But hang tight cuz it only takes that one person to see this.

 

[Oly]

There is a graph in here somewhere that details the FC loss over time from sunlight at different CYA ppm levels. It is not a straight line relationship. FC losses are rapid and very high at 0 ppm CYA and up to 30 ppm CYA the FC loss is reduced dramatically. Beyond 30 ppm CYA the savings improves but as you move higher the savings are much less. When I dosed with liquid my ideal CYA was 40ppm verified by testing daily FC loss and my target was 6pm. Now with a SWG I am beyond 60ppm CYA but not 70 and running my FC at 9. My daily FC loss is the same as my liquid days. Each pool is unique, use your test kit to dial in your system.

 

[mknauss]

There is a graph in here somewhere that details the FC loss over time from sunlight at different CYA ppm levels.

 

[RonsPlc]

I have found with my setup, (Stenner dosing the pool twice a day), that My FC usage is the best with a CYA of 60.
At 6pm I am right where I need to be for the next dosing, scheduled for 6:15-6:40.
But as stated by Oly, each pool is a bit different.

 

[jalapenopopper]

View attachment 359778

What is the right axis in the chart? Thanks for sharing.

 

[mknauss]

There is no value to the right axis

 

[Sunnydaze]

I don't have much to add except that I see a noticeable increase in FC consumption when my cya drops to 50 from 60 in this AZ sun. I haven't tried 70 but I have doubts it would get me much less than the 3ppm loss per day I'm seeing now.