CYA for Salt Chlorinator Pools II

[waterbear]

Here is the CYA article about plaster and CYA:

http://findarticles.com/p/articles/m...4/ai_n15932555

Although this probably applys more to very high CYA, this was why I was reluctant to go to higher CYA levels. I may end up going a bit higher anyway.

The sudy was done by ARCH chemicals! These are the same people who put copper into trichlor pucks. I am sure they are talking about CYA levels well above 100 ppm! There is also evidence that sulfates from using dry acid can affect the plaster so there can be multiple causes for damage to the plaster finish. The article did state that ARCH chemical recommeded switching between trichlor and other forms of chlorine to keep stabilzier levels from going too high. Does this mean that they are starting to read the Pool Forum? Seem like THAT piece of advice has been given on here for a very long time!

[dep78737]

Looks like the SWG manufacturers understand their products better than we do. It's in their best interest to suggest CYA/CL levels that will work in a vast majority of pools, otherwise people would be cursing them instead of singing their praises. Partially based on advice in this forum, my CYA was around 40 last year and I kept having to crank up the output. Raised it to 60 this year and now run at 40-50% instead of 60-70%. FC levels are more stable and acid use is down also, maybe since it's working less and maybe since the plaster is now 2 yrs old.

[waterbear]

If your cell output is down your pH should not drift up as quickly since you are manufacturing less sodium hydroxide! Another reason to run the cya a little higher! Actually, your results are pretty typical of the things I have seen with my customers when viewing their histories. The vase majority of them bring water in for testing weekly or bi weekly and the LaMotte software we use allows me to graph test results which makes spotting these trends easy to see. (Now you all know what I do when I get bored at work!)

[bbb]

Great thread - thanks to everyone posting.

For what it's worth - I'm on my first year with a Pool Pilot, and *have* been able to keep FC in the pool even with CYA in the 30 range (28K gallon pool, 48 size cell, power level 2, 20% to 33% usage). I have been debating about where to keep my CYA levels, too. I have kept my new solar cover on at all times this year except for when we actually are using the pool. One theory is that my blue/silver solar cover has helped me maintain a higher FC level in the pool, since there is less sunlight hitting the water. I chose blue/silver because I wanted to preserve heat from my heat pump.

However, thanks to all these discussions, and the fact that we are now in full summer "school is out" mode - meaning more time with the cover off and a higher bather load) I bought 2 bottles of hth brand CYA at my local hardware store to raise the level to around 50-60. Interestingly, the hth bottle is starting to warn people of CYA levels -- it says 20-40 is ideal, and it also says that chlorine effectiveness is severely limited over 100.

One other boast - I used plenty of borax to stabilize my ph last year, and added more this spring. My ph has been constant at 7.2 all year! My theory - lots and lots of acidic rain in the Northeast this year. So I expect the ph to eventually drift up -- although we have rain in the forecast for each of the next 7 days...

Related boast - between the rain and the solar cover, I have not added one drop of water to the pool - on the contrary, I have had to drain inches off several times!

Final boast - 2nd year of bbb, perfect water every day this year - nothing added to pool except bleach (pre-SWG), polyquat (early spring, to make sure no algae before the cover came off), baking soda (to bring my alk up in early spring), and borax (pre-SWG, to bring ph up to 7.4, though it never moved)

last reading:
FC 3
CC 0
CYA 30 (will raise to around 60 for SWG, but no worries)
TA 90 (may raise with some baking soda, but no worries)
ph 7.2
salt 4400 ppm (overcalculated when I added it for the SWG; no worries)
calcium - doesn't matter - vinyl pool with titanium core heater

[mas985]

Ok, I think I am convinced. I will try a CYA level closer to 60 ppm. It will be interesting to see how much the CL level rises with a CYA rise.

[mas985]

Last week I raised my CYA from 30 to about 55. After a week of running with the higher CYA, I have come to the conclusion that it had no affect on my residual chlorine level. During this week I did not change my pump run time or the chlorinator setting. Also, pool temp and PH where about the same.

CL = 2 ppm @ CYA 30 ppm
CL = 2 ppm @ CYA 55 ppm

So the graphs from the CYA study are correct in that chlorine retention does not increase significantly for CYA levels more than 25 ppm even for a SWG pool.

One other question. Assuming the same residual, is a SWG any different than an ORP controller with liquid chlorine? Both would need to add chlorine to the pool at the same rate for the same residual. To me at least, once you get past the chlorine injection method, there is no difference. Therefore, why should the CYA levels be any different? Also, the argument about shocking in the cell for SWGs also applies to the liquid chlorine. The chlorine concentrations would be just as high near the injection point.

Sorry for keeping the debate going but there seems to be a lot of conflicting information, theories and experimental results.

[waterbear]

Last week I raised my CYA from 30 to about 55. After a week of running with the higher CYA, I have come to the conclusion that it had no affect on my residual chlorine level. During this week I did not change my pump run time or the chlorinator setting. Also, pool temp and PH where about the same.

CL = 2 ppm @ CYA 30 ppm
CL = 2 ppm @ CYA 55 ppm

So the graphs from the CYA study are correct in that chlorine retention does not increase significantly for CYA levels more than 25 ppm even for a SWG pool.
but you are still not within the recommend range of 60-80 ppm. Try raising it up to 70 ppm and see what happens. I find that I lose chlorine quickly when my CYA is below 60 ppm and even 60 is iffy.
One other question. Assuming the same residual, is a SWG any different than an ORP controller with liquid chlorine? Both would need to add chlorine to the pool at the same rate for the same residual. To me at least, once you get past the chlorine injection method, there is no difference. Therefore, why should the CYA levels be any different?
Because the FC levels in the cell when the cell is generating are VERY high. It is not just shock level...more like 'supershock' level. The level is much higher than can be achieved by manual chlorination!
Also, the argument about shocking in the cell for SWGs also applies to the liquid chlorine. The chlorine concentrations would be just as high near the injection point.
No, it would be MUCH higher with a SWG which is generating chlorine gas which then dissovles in the water to form hypochorous acid. If you had an automated chorine gas injection system that was introducing the gas into a very small chamber of water (the size of a generator cell) it might be similar but a dosing pump with liquid chlorine will not reach the same concentrations nor will it come close.

Sorry for keeping the debate going but there seems to be a lot of conflicting information, theories and experimental results.

Hope this helps.

[waste]

Hi all, esp Karin who started this (I'm going to TRY not to rant) Karin, the tech did lie to you, chlorine is chlorine is chlorine - Pat and Evan might be on to something with the introduction method, but the chlorine is the same (and made the same way most chlorine sold is made, be it a gas, puck, liquid or granual).
My problem has always been with the reason for a higher cya for salt pools, the reason proffered by Pat and Evan is about as intellectually satisfying as a ricecake satisfies a dieter. They understand chemistry a LOT better than I, but it sounds like they're quoting chapter and verse from the SWG makers. I started a rant down in the "China Shop" about this (and something else), yet none of this was brought up. So what if you are super, super shocking the water as it passes through an energized cell? Killing combined chlorine is one of the things we all do when we add bleach (chlorine) to the pool, it just does a better job of it. If it takes the entire production of cl to counteract the cc, the unit isn't dialed up enough (though I doubt that cc takes all the cl that's being produced). If it's the uv that is stealing the cl, cya will help that, but at the same time, the kill time for ... yuckies is reduced, people who follow Ben's Best Guess won't be able to generate enough to satisfy it's requirements - if you're saying that BBG doesn't apply to SWG's then SAY SO, Ben is an intelligent person and if you have data that contradicts his 'best guess', he'll probably welcome it and ammend the BBG to reflect that. I, until I hear otherwise, will follow the Best Guess and keep my pool owners @ 30 -40 cya, because they won't (or can't) understand that violating all the literature they've recieved and instructions they've been given, will be a good thing (they are pool store zombies and cl > 3 ppm = BAD). Are you sure that the SWG manufacturers aren't just trying to get people to generate more cl - they'd sell a lot more replacement cells if every one they sold had a longer run time? I hope I haven't ranted here, just a few points that came to mind as I read and reread this topic.
mas985, thanks for the link, now I know that Arch is within 1/2 hr from me, I'll gladly accept donations for an assault rifle and ammo, and a defense fund to protect me when I go down there and 'set them straight'

[Lenny]

waste,

Doesn't it make sense to try the 60 to 80 CYA range and see how it works with a SWG? If the manufacturers, etc. have determined that the super chlorination of the water as it passes through the cell helps reduce the need for active chlorine (not tied up by CYA) in the pool than why not give it a whirl? The important thing is to keep algae and other nasties at bay so if people are running their SWGs sucessfully in the 60-80 range and not reporting any problems than there must be something to it.

If we run with a CYA under 60 than the cell would need to work harder to sustain a given residual chlorine level, which should shorten the cell life. So it's not a matter of the manufacurers trying to sell us more replacement cells.

I just installed a SWG so I'll see how it goes while follwing the manuf. suggestions. Otherwise, I might be shortening the cell life unnecessarily.

[waterbear]

Hi all, esp Karin who started this (I'm going to TRY not to rant) Karin, the tech did lie to you

I have to disagree with this!

, chlorine is chlorine is chlorine - Pat and Evan might be on to something with the introduction method, but the chlorine is the same (and made the same way most chlorine sold is made, be it a gas, puck, liquid or granual).
My problem has always been with the reason for a higher cya for salt pools, the reason proffered by Pat and Evan is about as intellectually satisfying as a ricecake satisfies a dieter. They understand chemistry a LOT better than I, but it sounds like they're quoting chapter and verse from the SWG makers. I started a rant down in the "China Shop" about this (and something else), yet none of this was brought up. So what if you are super, super shocking the water as it passes through an energized cell? Killing combined chlorine is one of the things we all do when we add bleach (chlorine) to the pool, it just does a better job of it. If it takes the entire production of cl to counteract the cc, the unit isn't dialed up enough (though I doubt that cc takes all the cl that's being produced). If it's the uv that is stealing the cl, cya will help that, but at the same time, the kill time for ... yuckies is reduced, people who follow Ben's Best Guess won't be able to generate enough to satisfy it's requirements - if you're saying that BBG doesn't apply to SWG's then SAY SO, Ben is an intelligent person and if you have data that contradicts his 'best guess', he'll probably welcome it and ammend the BBG to reflect that. I, until I hear otherwise, will follow the Best Guess and keep my pool owners @ 30 -40 cya, because they won't (or can't) understand that violating all the literature they've recieved and instructions they've been given, will be a good thing (they are pool store zombies and cl > 3 ppm = BAD). Are you sure that the SWG manufacturers aren't just trying to get people to generate more cl - they'd sell a lot more replacement cells if every one they sold had a longer run time?

Here is where your rant falls apart. I test a lot of water and I can tell you that raising the CYA into the 60-80 ppm range allows you to turn the output DOWN on the cell...not up! I have oberved with my own system that when the CYA drops to about 50 ppm I have to almost double my run percentage!

I hope I haven't ranted here, just a few points that came to mind as I read and reread this topic.
mas985, thanks for the link, now I know that Arch is within 1/2 hr from me, I'll gladly accept donations for an assault rifle and ammo, and a defense fund to protect me when I go down there and 'set them straight'

I guess we're headed for the china shop again!