CYA Problems

[maureenq]

I tested my water yesterday (25,000 gal guinite pool)and the pool co. is here right now opening it up. I decided after last year when the pool co. opened and I purchased the "start-up chemicals" from them, not to buy them again since last year after they left I tested the FC and it was 0. Anyway, here are my #'s - FC,CC, TC -0
PH - 7.8
ALK - 120
Cal - 150
Cya - 55
Besides adding bleach, I think everything else looks ok, based on my #'s from last year. My cya has run the same all last year, but this year to cut down on bleach usage, I want to drain some of the water to see if that will make a difference. We have a community well, which still has to meet the water co. standards, but I assume I should have my reg. water checked first and see if this will cause a problem. I had it checked before and the only thing that was found was a high metal content, I know this since I had to buy a water system since my hair was turning green. Anyway, does this effect the cya or not? How much should I drain at a time? Since I had to have the water trucked in so as to not drain the community system, I can't add too much from my hose at a time. Also I usually use algacide 60 poly and think because of high metal content in my water, I should use some additive to help with this. Any advice would be appreciated. Thanks!!

[chem geek]

You will only be cutting down on your bleach usage with the lower CYA if you maintain a somewhat lower FC level with that lower CYA. At 55 ppm CYA if you were maintaining around 6 ppm FC with an absolute minimum of 3.7 ppm FC, then at a lower CYA level of 30 ppm you could maintain 3.5 ppm FC with an absolute minimum of 2.2 ppm FC. Since you may lose up to half of the FC over a day, the old way you might have added 5 ppm FC or so each day while with the lower CYA you will be adding around 3 ppm FC or so each day.

High metal content will not affect CYA or anything else except that it can cause staining. Since it turned hair green, this sounds like copper rather than iron. In either case, you can use a metal sequestrant such as Pool Magnet Plus or another brand.

You technically should not need to use PolyQuat 60 if you maintain chlorine levels, but you can use it as an insurance policy just in case your chlorine levels drop (say, if you forget to add chlorine for a day). If you get it at a good price, then it will ensure you won't get algae, but just keep in mind that it isn't necessary if chlorine levels are maintained.

Richard

[nater]

I would leave the 55 CYA alone. I've battled very high CYA (120+), and you can succesfully keep the pool clean and clear, even at very high levels by following the best guess chart. In my opinion, if it ain't broke, don't fix it. Especially with the issues it sounds like you have with fill water.

Have you considered a SWC unit? You're at the right cya level for one, and you won't have to lug bleach anymore...

[jagwire22]

Can someone straighten me out in lamens terms?

I thought had had most everything figured out, now I think I am confused again !!!


25000 gallons
Chlorine - pool store said 1ppm, Wal-Mart test kit said around 6ppm
(is the difference caused by one measuring FC,TC,CC and the other measuring FC,TC,CC) I have know idea!!!!!!!
CYA - 20
PH - 7.7
TA - 120

I know cya stabilizes the the chlorine level, but If it takes less bleach to sanitize a pool with a lower CYA then why would I want to raise my CYA to 30-50ppm like most people suggest.

Will I add less bleach in the long run with CYA at 30-50ppm compared to CYA at 20ppm?


Thanks in advance!!!!

[waterbear]

Can someone straighten me out in lamens terms?

I thought had had most everything figured out, now I think I am confused again !!!


25000 gallons
Chlorine - pool store said 1ppm, Wal-Mart test kit said around 6ppm
(is the difference caused by one measuring FC,TC,CC and the other measuring FC,TC,CC) I have know idea!!!!!!!
CYA - 20
PH - 7.7
TA - 120

I know cya stabilizes the the chlorine level, but If it takes less bleach to sanitize a pool with a lower CYA then why would I want to raise my CYA to 30-50ppm like most people suggest.

Will I add less bleach in the long run with CYA at 30-50ppm compared to CYA at 20ppm?


Thanks in advance!!!!

CYA helps prevent the chlorine from being burned off by sunlight. If it is too low you might go thorugh more bleach trying to keep the level up than if you have the proper level in your pool. If you have too much the chlorine becomes less effective at santizing and destroying algae. 30-50 ppm works well in most outdoor pools (60-80 in pools with a SWG).
Hope this helps.

[bcb1]

55ppm CYA is no big deal at all. Mine usually runs in the 70-80ppm range, and I've always had crystal clear water, never a problem.

I've often heard that 30-40ppm of CYA is the conventional wisdom, but I can tell you for sure that twice that amount works just fine. I've been at the pool store and those guys have told me that they only have seen "chlorine lock" problems when the cya level is in the 150-200ppm range.

[chem geek]

Chlorine lock doesn't ever really occur in the sense that at some CYA level disinfection stops completely regardless of FC level. At higher CYA levels you simply need to have higher FC levels to maintain the same level of disinfecting, oxidizing and prevention of algae capability. With a lot of CYA in the water, it is possible to slow down the dissolving of slow-dissolving Trichlor (that happened to me when my CYA got over 100).

See this chart which really could continue on at even higher CYA levels having even higher Min FC levels.

The issue is that with higher FC levels at higher CYA levels you are wasting more chlorine because about half of the FC is going to get consumed by sunlight each day and half of a larger number is a larger number. However, as waterbear said, with too low an FC, you simply won't be able to stay on top of your chlorine fast enough. It's a tradeoff between chlorine waste (at higher CYA and FC) vs. how quickly and frequently you are able to replenish the chlorine level. Most people don't want to spend every hour by their pool adding more chlorine.

For SWG pools, there is a completely separate issue as to why higher CYA levels are required and this has to do with SWG cell efficiency, but that's discussed on this thread.

Richard

[CarlD]

Here's the piece that everyone's leaving out:

At higher CYA levels, yes, it's true, you need a higher FC level to maintain sanitation.

BUT what happens is that you get a residual of chlorine that generally remains, so you are only chlorinating for the extra you need.

Say, for example, your CYA is 110. The suggested FC for that CYA is 8 to 15 ppm (and shock at 25). You should find it very easy to keep your FC in this range and not use any more chlorine on a weekly basis to maintain it than you use at lower CYA and FC levels.

Actually, your chlorine usage may go DOWN because the CYA gives you such a high residual of chlorine.

One of the moderators, Aylad, leaves in the Deep South. She gets lots of factors that drive FC down (consuming her chlorine). So Aylad runs her pool consistently at higher CYA levels than we Northerners do--80ppm. Since Aylad has her FAS-DPD test kit, she can test higher levels of chlorine easily--and keeps her FC level in the 5-10ppm range. This allows her to avoid constant monitoring and chlorine additions several times a day.

But since I live in Northern NJ, I tend to keep my CYA in the 30ppm range for the early part of the summer, running it up to 40-50 when we approach the Dog Days.

CYA is a two-edged sword. It slows the metabolizing of chlorine, so it doesn't burn up instantly in the ultra-violet. But it slows down the metabolizing, so you need more chlorine. Still, if you follow the guidelines AND have the FAS-DPD test, there's no reason not to run higher levels of CYA. It CAN make your life easier if you have VERY intense UV (at lower latitudes), and/or lots of organic material you are metabolizing.

CYA should NEVER be used in an indoor pool.