CYA levels with a SWG

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Sam721

Sam721

Active member
May 18, 2022
25
Murfreesboro, TN
I have been lurking around for a while now and I have gotten a test kit 6 weeks ago or so. After reading the Pool School articles, most of the recommendations on balancing the water with a SWG make sense to me, but one question remains re CYA.

I currently have my CYA around 30, and my SWG is keeping a steady FC of 3.5 at 70% duty cycle, even at 100+ F air temps (water is around 90). Why would I increase the CYA further up to 60-70 that is recommended here if my SWG is keeping up? It'll only make it more difficult to do a SLAM if it is needed later.

Anything I am overlooking?

Here are my latest water test results:
FC 3.5
CC 0.0
pH 7.9
TA 75
CH 125
CYA 30
Salt 3100
Water Temp 88

Thanks in advance for the advice!
Sam
 
If it works for you, great. In most climates, a CYA under 70 ppm with a SWCG will spike the FC loss by 25-50%. It sure does in my pool.

If you maintain that low level, I would suggest you test CYA level every 2 weeks during swim season. It can degrade some, especially in water temperatures at or above 90F.
 
SWG cell's will generate a given amount (pounds) of chlorine in their life, then you will need to replace the cell. I couldn't find a life rating for your SWG cell.

With more CYA, you would be able to turn your SWG down further as you would lose less FC a day. So your cell would last longer before having to replace it.

SLAM not as much of a concern with SWG because its so much easier to keep your FC constant at a recommended level you really should not have to SLAM.

Randy
 
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Sam721 said:
I have been lurking around for a while now and I have gotten a test kit 6 weeks ago or so. After reading the Pool School articles, most of the recommendations on balancing the water with a SWG make sense to me, but one question remains re CYA.

I currently have my CYA around 30, and my SWG is keeping a steady FC of 3.5 at 70% duty cycle, even at 100+ F air temps (water is around 90). Why would I increase the CYA further up to 60-70 that is recommended here if my SWG is keeping up? It'll only make it more difficult to do a SLAM if it is needed later.

Anything I am overlooking?

Here are my latest water test results:
FC 3.5
CC 0.0
pH 7.9
TA 75
CH 125
CYA 30
Salt 3100
Water Temp 88

Thanks in advance for the advice!
Sam
Click to expand...
I find having mine higher means I can turn the % down on my salt cell, thus I hope I can extend the life. It also depends how much sun you have where you live. I'm in Vegas so the sun just eats my chlorine. If you're gonna ride it that low, I agree with mknauss above and would just test it more often.
 
Thanks to all! Your answers make sense: your SWG will last longer because there is less FC loss, and you have some more margin on the FC and don't need to be watching it as a hawk every day.

I'll say we do have a lot of sun here in TN, but also a lot of rain. So I need to watch the pool balance closely anyways because there are losses due to overflow.

Compared to last year (our first season after the pool was completed), I am running the SWG much less this year. Last year, I had to have it pegged at 100% for most of the hottest months. I was relying on the PB that year for testing the water and was blindly doing what they recommended. Compared to a lot of stories I've read here, I think our PB is probably one of the better ones. Our pool stayed sparkly clean and clear all summer with minimal effort (just adding salt pretty much, and a few pH adjustments). Their prices on the chemicals are almost on par with what you pay for them at the Home Depot and Lowe's for equivalent products, so they seem to be reasonable in that regard as well.
This year, I wanted to educate myself and understand better. The first logical step was to test the water myself and keep a log. It seems like the only thing the PB does different is CYA levels. They say anything above 10 is doing just fine. I told them I was going for a min of 30 and they told me that's fine and works, but not necessary in their opinion.
 
randytsuch said:
SWG cell's will generate a given amount (pounds) of chlorine in their life, then you will need to replace the cell. I couldn't find a life rating for your SWG cell.

With more CYA, you would be able to turn your SWG down further as you would lose less FC a day. So your cell would last longer before having to replace it.

SLAM not as much of a concern with SWG because its so much easier to keep your FC constant at a recommended level you really should not have to SLAM.

Randy
Click to expand...

So what happens when you host a party over the weekend and CC goes to 0.6PPM? Isn't the only way to get rid of CC is another SLAM? or else have CC 0.6 PPM lurking in your pool forever? MPS would only oxidize organics that were in your pool before a party... any CC after a party would stay CC...?
 
kaabob said:
So what happens when you host a party over the weekend and CC goes to 0.6PPM? Isn't the only way to get rid of CC is another SLAM? or else have CC 0.6 PPM lurking in your pool forever? MPS would only oxidize organics that were in your pool before a party... any CC after a party would stay CC...?
Click to expand...

Nothing. 0.6ppm (if you even want to check that accurately) is close to zero and not a big deal. Once it gets up to 1ppm is where you need to check things more closely and maybe raise chlorine a bit.
 
Last edited:
kaabob said:
So what happens when you host a party over the weekend and CC goes to 0.6PPM? Isn't the only way to get rid of CC is another SLAM? or else have CC 0.6 PPM lurking in your pool forever? MPS would only oxidize organics that were in your pool before a party... any CC after a party would stay CC...?
Click to expand...
If it was me, I'd up my SWG output a little in advance of the party to get FC a bit higher. Its still safe, and I don't think anyone could tell the difference if you were up at 10ppm instead of 6ppm (this is assuming CYA of 60).
So you'd have more of a buffer and shouldn't go so low .

Randy
 
randytsuch said:
If it was me, I'd up my SWG output a little in advance of the party to get FC a bit higher. Its still safe, and I don't think anyone could tell the difference if you were up at 10ppm instead of 6ppm (this is assuming CYA of 60).
So you'd have more of a buffer and shouldn't go so low .

Randy
Click to expand...
Gotcha... but wouldn't CC still be around and never be freed up until another SLAM? I though SLAM was the only way to zero out CC
EDIT: maybe throw in a bag or two of MPS half an hour before the party since I have those lying around and have that oxidize organics instead of FC attacking it
 

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kaabob said:
Gotcha... but wouldn't CC still be around and never be freed up until another SLAM? I though SLAM was the only way to zero out CC
EDIT: maybe throw in a bag or two of MPS half an hour before the party since I have those lying around and have that oxidize organics instead of FC attacking it
Click to expand...
For future reference MPS will cause you to be unable to test for CC. Hint: don’t use MPS in a pool.

CC’s will float around between 0 and 0.5 all season long. I almost never test for them only because they are always 0.5ppm or less.
 
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