CYA for Salt Chlorinator Pools II

[tonyl]

Well for our pool my output is up a bit this year due to the hot hot summer so far here in the midwest. I'm at 50% and 8 hours per day. Water temp is 91.

Edit: forgot to mention it's more efficient to run with salt at the higher end (3400), your output is also dependent on the salt level.

[rbonin]

The high recommended CYA level by most salt water chlorinator manufacturers seems to be a mystery to most on this forum.

I abide by Ben's "best guess" chart of CYA vs. FC and so I keep my pool at 40ppm CYA and about 5ppm FC. My Polaris AquaClear cell runs 10 hours a day as my pool is in direct sun all day.

[cwstnsko]

Agree with the previous post about following Ben's guidelines. I run my CYA at about 30 ppm. I adjust the SWG so that my FC is at about 5 ppm in the morning, and it drops no lower than 3 ppm by late afternoon in full AZ sun. I run my pump on low speed 24/7, SWG at about 30% on power level 1, salt is at 2900-3000.

[Karin]

I've heard that using my SWCG to shock will hasten the cell's life expectancy. I don't want to hasten its demise and will probably use good ole bleach on the occasions it may need some shocking--after heavy rains.

I can only run my pump at one speed. It can adequately turn my water in a 4-6 hour period, but I leave it on for 6-8 hours....it usually starts at 8am. Should I maybe have it start later in the morning so that it runs during most of the hot afternoon part of the day and keeps adding fresh chlorine that way?

Based on your comments, I'm leaning toward a CYA of around 50---close to Ben's recommendations and also Aqua Rite's. How's that for straddlin' the fence?

Tell me more about CYA staining??? I added some the other day through the skimmer---tried to dissolve it with some warm water first, but that stuff doesn't like to dissolve, and then slowly poured it into the skimmer while it gulped it down.

I presently have some yellowish stains in corners and the risers of the steps and along the walls in the deep end that appear to be recent. Since we just had it resurfaced with some Diamond Brite in March, I'm very concerned.

We had a bout of yellow algae about a week ago---which I think is gone. (Cleaned the filter daily.)
We did a partial water change to lower the CYA only to find out that the city water was full of phospates....plus I forgot to add a sequestering agent till after it had been filled. Then after going to 4 pool stores and getting 4 different CYA readings of : 15, 25, 30 and 60 all from the same sample, I added some CYA to bring it up to 40. Yes....I do need a life...

So now I'm wondering what the culprit is for the stains:

From the Yellow algae?
From the new water full of phosphates etc?
From the additional CYA?

Other than for the stains, the pool and water look great: clear and blue....sigh..I should be in there right now instead of typing about it....
FC 6.5
TC 6.5
PH 7.4
Hardness 200ppm
Alkalinity 100
CYA 40
Salt 3100

[Simmons99]

I've never heard of CYA staining - it could be due to metals or algae

[PatL34]

Karin & Others,

The 60 - 80 ppm CYA recommended by the SWCG manufacturers is because the cell instantaneously creates a high concentration of chlorine, and kills the chloramines as well.

Without the high CYA, the chlorine would be used up rapidly before it gets into the body of the pool.

With my SWCG, a 50 - 60 ppm CYA level appears to work fine. So 50 ppm you are using is in the ballpark.

Regarding the staining, it could well come from your fill water, but others with more experience can help you. Have you tried to brush this stain? To my knowledge CYA does not stain, otherwise we would be using something else.

Your water chemistry apart from the CYA is also in the ballpark, and I can well understand your frustration with 4 pool stores giving you different readings, so I take them with a pinch of salt (pun intended) They do not know how to be consistent. Once you do it yourself the same identical way each time, you will be less frustrated

mas985, I would use option #2, based on what I said at the beginning. The cell should produce the chlorine regardless, and if not you can always aise the output. A bit of trial & error. I have not heard of CYA dissolving plaster pools. That's a new one to me. Will have to investigate.

Hope this helps.

Pat

[Karin]

Well, I went to the horse's mouth and called up Aqua Rite to ask them about their higher recommended CYA levels. After 10 minutes of listening to some vintage elevator music, the rep told me that the chlorine that a SWCG makes is different than the regular chlorine you just add to a pool.

That's why they want a higher CYA---to protect it from sunburn.

Was she just trying to get me to hang up, or does that sound plausible? Hmmm...

[tonyl]

I think you'll have to experiment a bit on your CYA levels. I keep mine within the recommended range due to full sun exposure. I think most pools would be fine with 50ppm and after all, stabilizer isn't cheap.

[waterbear]

Well, I went to the horse's mouth and called up Aqua Rite to ask them about their higher recommended CYA levels. After 10 minutes of listening to some vintage elevator music, the rep told me that the chlorine that a SWCG makes is different than the regular chlorine you just add to a pool.

That's why they want a higher CYA---to protect it from sunburn.

Was she just trying to get me to hang up, or does that sound plausible? Hmmm...

She told you the same thing that PatL34 stated above and the same thing that I have stated in other threads. There is a difference between manually chlorinating and producing chlorine by electrolysis. I have spoken to tech support at Goldline Controls, Poolsean, who is in this forum and works for AutoPilot Systems (Pool Pilot SWG's), and some of the dealer literature that I have access to from my job (the store I work at sell several brands of SWGs) all are saying the same thing. It is better to run the CYA level higher in a pool with a SWG. I run mine at 70 ppm with my Aqualogic PS-8 (Goldline Controls). I also test a lot of water all day and can access histories of test results. About half our customers have SWG's installed and there are several that have been running CYA at 30-50 ppm. I have notices that these people have not been able to maintain adequite FC levels, run their cells at very high outputs, and some have had problems with algae blooms, including Mustard Algae. I have not seen any of these problems in the ones running higher CYA levels and keeping the FC at about 3 ppm or slightly higher. It is a small sample, maybe about 50 or 60 customers but the trend I have seen is unmistakable!

[mas985]

I am interested in everyone's settings as well, since there seem to be many different lines of thinking on this:

1) Use recommended CYA 60-80 and keep chlorine level per Ben's CYA table.
2) Use recommended CYA 60-80 and ignore Ben's CYA table and rely on cell to continuously shock water plus add bleach when necessary.
3) Use lower CYA level and Ben's CYA table. Recent studies indicate the CYA can contribute to dissolving plaster and shortening it's life.
4) Use lower CYA level, ignore Ben's CYA table and rely on cell to shock water.

My current preference is #4 since I have a plaster pool and not quite at Ben's CL ppm. I am operating at a CYA of 30, 21000 gallon pool, setting 90% and run the pump 6 hours a day. I am able to maintain 2 ppm. I have calculated that with my current settings, the cell puts in about 2 ppm per day so I figure I am using up 2 ppm per day.

If anyone is interested, the aquarite/logic cell puts in 1.45 lbs/day @ 100% setting. This is equivalent to 1.45 gallons of 12.5% bleach.

I think if I upped the CYA with the current settings, the chlorine would probably rise but not as quickly as per Ben's table. I am trying to research this a bit more to see if I can predict a chlorine ppm level with different CYA levels. I would love to experment with different CYA levels but given the difficulty of reducing CYA, this is not an option.