CYA and water chemistry questions

[IN DEPTH]

It seems that my account doesn't have the privileges to start a new conversation in order to send a private message to a member. It's been a few days since I emailed the webmaster for support and I haven't received a reply, so I'm trying this approach.

I really enjoyed reading the technical details covering CYA and water chemistry. I would like to pose some questions regarding the release of chlorine from chlorinated cyanurates.

What is the mechanism that triggers the release of chlorine or HOCL in response to a demand such as a testing reagent or algae?
CYA:FC difference between bodies with a SWCG and any other means of chlorination is dramatic. Is this due to the small but constant rate of production of the SWCG to effect a stacking of shielded sanitizer within a high concentration of CYA or is the salt cell actually producing more chlorine due to the rapid reaction with CYA?
If any other means of chlorination were to simulate the same production and feed rate of an SWCG such as chlorine gas or bleach, would the same effect be expected?
Is the tapering off of free chlorine in manually dosed pools the reason to maintain a minimum of CYA?
Does UV exposure have any effect on the formation of chlorinate cyanurates?
Why am I finding that water with 80 to 100ppm CYA and overwhelmed with algae will hold 5ppm free chlorine for 12 or more hours (and not be quickly reduced or affect the algae)?

 

[Leebo]

Been trying off and on to email however keep getting them returned. You can use the following URL

https://www.troublefreepool.com/conversations/add

 

[ajw22]

Welcome to TFP.

It seems that my account doesn't have the privileges to start a new conversation in order to send a private message to a member. It's been a few days since I emailed the webmaster for support and I haven't received a reply, so I'm trying this approach.

The forum requires posting a few messages before you are allowed to start private converdations. This is to prevent spamming of members by bots.

Why am I finding that water with 80 to 100ppm CYA and overwhelmed with algae will hold 5ppm free chlorine for 12 or more hours (and not be quickly reduced or affect the algae)?

5 ppm of FC with CYA 100 is using a firecracker against the Army. Ineffective firepower.

SLAM FC for CYA 100 is around 40ppm to be effective.

The Free Chlorine and Cyanuric Acid Relationship

Managing your cyanuric acid and Free Chlorine levels is key to stabilizing your pool. Learn how these two items affect each other.

www.troublefreepool.com

CYA - Further Reading

www.troublefreepool.com

CYA Chlorine Relationship - Further Reading

www.troublefreepool.com

 

[mgtfp]

What is the mechanism that triggers the release of chlorine or HOCL in response to a demand such as a testing reagent or algae?

There is no real trigger. These are so called equilibrium reactions, very common in chemistry. These are not static equilibriums, but dynamic ones.

Both reactions, the formation of chlorinated Cyanurates and the release of chlorine into HOCl, are constantly happening, never stopping.

The reaction rates are proportional to the number of reaction partners. If there is an "excess" of HOCl, then the formation of chlorinated Cyanurates is happening faster than the release of chlorine from Cyanurates. Eventually, both reactions are happening equally fast. From the outside it looks like the amounts of chlorinated Cyanurates and of HOCl are not changing, but there's still a constant back and forth going on.

If a few HOCl get "used up" by killing algae, the equilibrium is disturbed and the release of chlorine from CYA is happening a bit faster than the formation of chlorinated Cyanurates until a new equilibrium is reached.

 

[mgtfp]

CYA:FC difference between bodies with a SWCG and any other means of chlorination is dramatic.

The constant and reliable chlorination with a SWG reduces the risk to slip below min FC and allows maintaining lower FC/CYA. But we generally don't recommend to actually do so. It is much easier to maintain a SWG pool in the higher target FC range with wiggle room for changing FC demands based on bather load, cloud coverage and changing UV-load over the seasons.

Maintaining a SWG close to the minimum FC is theoretically possible, but ends up micromanaging the pool. You have to test very often and readjust the SWG output.

Much easier to aim higher, adjust the SWG output so that you are maybe in the lower to mid target range on high UV days and accept that FC creeps up on more cloudy days. Any FC up to SLAM-FC for current CYA level is safe to swim in.

See FC/CYA Levels.

 

[mgtfp]

Is the tapering off of free chlorine in manually dosed pools the reason to maintain a minimum of CYA?

Without any CYA, FC burns off very quickly under UV-light.

Without CYA you are also missing its moderation effects of chlorine's harshness. Note that without CYA, an FC of about 0.64ppm is equivalent to SLAM-FC with CYA in the water, for example FC 16ppm for CYA 40ppm.

Target FC would be something like FC 0.1ppm without CYA. This would be very challenging to maintain in a residential backyard pool.

 

[mgtfp]

Does UV exposure have any effect on the formation of chlorinate cyanurates?

UV predominantly triggers decay of hypochlorite ion (OCl^-) into chloride Cl^-. That means all the equilibriums have to reshuffle, some HOCl turns into OCl^-, and some chlorinated Cyanurates release some chlorine into HOCl and OCl^-.

 

[xDom]

The constant and reliable chlorination with a SWG reduces the risk to slip below min FC and allows maintaining lower FC/CYA. But we generally don't recommend to actually do so. It is much easier to maintain a SWG pool in the higher target FC range with wiggle room for changing FC demands based on bather load, cloud coverage and changing UV-load over the seasons.

Maintaining a SWG close to the minimum FC is theoretically possible, but ends up micromanaging the pool. You have to test very often and readjust the SWG output.

Much easier to aim higher, adjust the SWG output so that you are maybe in the lower to mid target range on high UV days and accept that FC creeps up on more cloudy days. Any FC up to SLAM-FC for current CYA level is safe to swim in.

See FC/CYA Levels.

You say that any FC level up to SLAM level is safe to swim in. I understand that when we SLAM it’s the ratio increase that’s important.

Keeping the ratio constant could we say that there would be no noticeable difference to a swimmer as FC raises?

So, a CYA of 10 and an FC of 0.75 won’t feel any different than a CYA of 100 and an FC of 7.5.
Would You agree with this?

 

[mgtfp]

So, a CYA of 10 and an FC of 0.75 won’t feel any different than a CYA of 100 and an FC of 7.5.
Would You agree with this?

Yep that's pretty much correct. There are some deviations from the linear correlation that HOCl is proportional to FC/CYA once you go to very high FC or very low CYA.

But all the different SLAM levels for different CYA levels in the FC/CYA Levels are equivalent to the same HOCl concentration. Without CYA in the water, SLAM-FC is equivalent to FC of about 0.64ppm.

 

[xDom]

Yep that's pretty much correct. There are some deviations from the linear correlation that HOCl is proportional to FC/CYA once you go to very high FC or very low CYA.

But all the different SLAM levels for different CYA levels in the FC/CYA Levels are equivalent to the same HOCl concentration. Without CYA in the water, SLAM-FC is equivalent to FC of about 0.64ppm.

Any chance you could link the chart that shows the quantity of HOCL to FC equivalency as it rises with CYA?
( if this makes sense! )

 

[xDom]

Yep that's pretty much correct. There are some deviations from the linear correlation that HOCl is proportional to FC/CYA once you go to very high FC or very low CYA.

But all the different SLAM levels for different CYA levels in the FC/CYA Levels are equivalent to the same HOCl concentration. Without CYA in the water, SLAM-FC is equivalent to FC of about 0.64ppm.

its fine, i found it in the opening page of Chem Geeks's posts, thank you

 

[IN DEPTH]

Welcome to TFP.



The forum requires posting a few messages before you are allowed to start private converdations. This is to prevent spamming of members by bots.



5 ppm of FC with CYA 100 is using a firecracker against the Army. Ineffective firepower.

SLAM FC for CYA 100 is around 40ppm to be effective.

The Free Chlorine and Cyanuric Acid Relationship

Managing your cyanuric acid and Free Chlorine levels is key to stabilizing your pool. Learn how these two items affect each other.

www.troublefreepool.com

CYA - Further Reading

www.troublefreepool.com

CYA Chlorine Relationship - Further Reading

www.troublefreepool.com

I’ve tried to post a few messages. They are either removed, heavily edited or I get banned. I was just banned a while ago for not having any posts!

I also just tried to post to a thread were a person in Arizona is having trouble with an indoor pool FC under an IC SWCG. I just asked questions like “is the pool losing water” and “what’s the bather load” and then gave the manufacturer’s instructions to review the salt cell hour counter and checking FC at a return to validate chlorine production and level. I basically just asked questions. The post never made it to the thread. I assume the moderators muted it.

It seems that if I post about my experience such as “the solution is dilution” I get redacted or muted by admins due to not being “part of the TFP method.”

I get the TFP method and while it does work, there are other ideas and methodologies that produce results (that aren’t that deviant from the TFP method).

Silencing ideas isn’t cool. Tag my post as not being in-line with TFP, but to burn my post is quite concerning in today’s age.

I respect the forum and use it a lot for equipment related issues and some chemistry like stains (sulfamic acid) and CYA discussions.

When I referred to 5ppm FC within a pool with 80-100ppm CYA, I was referencing an observation.

I totally understand the CYA/FC ratio as suggested by CMAHC (The Council for the Model Aquatic Health Code) and TFP.

However, there is supposed to be a trigger that releases chlorine bound to CYA kinda like on demand (if I’ve read this correctly on TFP).

My observations over a countless number of green swimming pools has shown me that pools with heavy algae and high CYA require either immense amounts of chlorine daily (FC/CYA ratio at shock level) or heavy dilution to reduce the CYA concentration pre-superchlor.

I’d have to review my accounting records but, I believe I’ve recovered at least 25 very green pools this swim season using the dilution approach. I do, however, serve an area where water is rather inexpensive.

I also point each an every pool owner to TFP to validate what’s going on so that it’s not just my word.

So, based on my observations, CYA at high levels can store chlorine to the point that 5ppm FC will have observably zero effect on algae AND the the FC will remain in the water far longer than expected (due to algae and very high demand for oxidation/sanitation).

However, in clear pool water, 60-80ppm CYA with 1-3ppm FC will maintain the water (assuming that heavy dilution from rain doesn’t happen or the cell doesn’t enter inspect mode, etc etc).

I’m trying to get to the mechanism that releases chlorine bound to CYA.

I assume that there is a minute amount of redox happening with green pools which is enough for clear pools but insufficient for pools in distress.

This leads me to believe that there’s either a photo-reactive element happening where the release happens with variations in UV exposure or the chlorinated cyanurate is the sanitizer (weak).

I just find it difficult to wrap my head around the chlorinated cyanurate just knowing when to allow production of HOCL due to demand. There must be an equilibrium situation or some other mechanic that effect the release (like the lack of UV).

It makes much more sense that the chlorinated cyanurate is just maintaining an equilibrium irregardless of sanitation demand (but in direct relation to use). However, when I see 5ppm FC holding in a green pool for several hours, it throws me off. The equilibrium is fully skewed and, therefore, the release of chlorine from CYA should be so that all of the FC is used within 12 hours or less.

If the mechanism could be identified more clearly, it may be able to be controlled in a way that allows for higher concentrations of CYA to shield FC from UV while also allowing for uninhibited use of FC. This could help reduce water use in dilution and really help with troubleshooting pool water on a large scale.

 

[duraleigh]

there are other ideas and methodologies that produce results

I agree, However that is not the purpose of TFP. TFP teaches a method of pool care that thousands upon thousands of people have proven works.

Our purpose is NOT to teach other methods or argue about the merits of TFP.

TFP is a collection of knowledge, methods and processes that work.......time after time.

"If it ain't broke..." *

* Off the subject. but the military refined that to be, "If it ain't broke, keep on fixin' it until it is!)

(

 

[IN DEPTH]

There is no real trigger. These are so called equilibrium reactions, very common in chemistry. These are not static equilibriums, but dynamic ones.

Both reactions, the formation of chlorinated Cyanurates and the release of chlorine into HOCl, are constantly happening, never stopping.

The reaction rates are proportional to the number of reaction partners. If there is an "excess" of HOCl, then the formation of chlorinated Cyanurates is happening faster than the release of chlorine from Cyanurates. Eventually, both reactions are happening equally fast. From the outside it looks like the amounts of chlorinated Cyanurates and of HOCl are not changing, but there's still a constant back and forth going on.

If a few HOCl get "used up" by killing algae, the equilibrium is disturbed and the release of chlorine from CYA is happening a bit faster than the formation of chlorinated Cyanurates until a new equilibrium is reached.

Exactly!

Equilibrium reaction along with redox.

However, the stated CYA:FC implies that the either the reactions are slow (which account for the increase in CT times relative to CYA ppm and not chlorinated cyanurate ppm) or that equilibrium isn’t the sole factor (or the equilibrium is being offset by something).

Based on observations, I have found that FC concentrations will remain higher with high CYA in green pools than low or zero CYA. Obviously, UV takes part but pool water recoveries (from algae) is a daily process. I’m seeing a much slower almost imperceptible reduction in FC at sub-shock levels with mid to high CYA with extreme demand.

The equilibrium is skewed heavily enough to reverse the reaction to HOCL production and exhaust the FC within the same time frame as water with little to no CYA (with only demand as a catalyst).

What’s the equilibrium constant between species? I get that it’s dynamic, but it’s gotta have something that induces a move/change/delta and also solves for an increase in CT and oxidation/sanitation effectiveness.

 

[IN DEPTH]

The constant and reliable chlorination with a SWG reduces the risk to slip below min FC and allows maintaining lower FC/CYA. But we generally don't recommend to actually do so. It is much easier to maintain a SWG pool in the higher target FC range with wiggle room for changing FC demands based on bather load, cloud coverage and changing UV-load over the seasons.

Maintaining a SWG close to the minimum FC is theoretically possible, but ends up micromanaging the pool. You have to test very often and readjust the SWG output.

Much easier to aim higher, adjust the SWG output so that you are maybe in the lower to mid target range on high UV days and accept that FC creeps up on more cloudy days. Any FC up to SLAM-FC for current CYA level is safe to swim in.

See FC/CYA Levels.

Totally agree!

I try to get at least a 2-3ppm FC with all of my SWCG pools. However, that target also requires a good deal of micro-managing. My clients are all hands-off but will heat the water and add water or have a pool party without telling me.

Running higher CYA works in the between times but complicates things when the pools catches use. I’m then getting 0.5-1ppm FC with high CYA and having to shock at incredibly high levels that causes all sorts of dumb stuff like granular cal-hypo sedimentation and cloudy water (cal-hypo).

Bather load, salt cell trouble (including turbo cell inspection shutoff) are very difficult to anticipate, so the idea becomes overdosing to account for unknowns. Higher CYA concentrations work but can cause a lot of problems if not managed based on a predictive model opposed to reactive (meaning staying ahead of CYA/FC ratio and demand).

This is why I tend to run 30-40ppm or less CYA, 3600ppm salinity, higher cell runtimes (60-80%), pump runtimes around 8-10 hours and hit the pool with 1.5-2lbs of 75% cal-hypo weekly (along with a temp pH reduction). None of my pools have pH management, so I run lower alkalinity and higher calcium hardness and let the pH go to 7.9 with a temp of 86-88°F. This works with LSI and reduces or eliminates calcium carbonate at the cell.

I’d much rather run higher CYA and get higher FC, but the fact is, for me, that it’s a liability.

I’m curious about less UV causing a stacking effect. I’m wondering if less UV not only reduces less FC but also retards the reaction between chlorine and CYA? In other words, is it a photo-reactive reaction?

 

[IN DEPTH]

Without any CYA, FC burns off very quickly under UV-light.

Without CYA you are also missing its moderation effects of chlorine's harshness. Note that without CYA, an FC of about 0.64ppm is equivalent to SLAM-FC with CYA in the water, for example FC 16ppm for CYA 40ppm.

Target FC would be something like FC 0.1ppm without CYA. This would be very challenging to maintain in a residential backyard pool.

I agree with the chemistry there, 100%.

However, pools have varying depths and areas of low circulation. I have pools where I can run a 1.0 and be perfectly fine. I also have pools with zero entries that will get spot algae without a minimum of 3ppm.

Basically, checking on the pool twice to three times per week is necessary to run minimums (less pump runtime, less FC, less cell runtime, less CYA). That model is ideal, but it’s not realistic for the vast number of pools out there (commercial or residential) or I’d be out of a job.

A vigilant residential pool owner that has the program down will be able to run a predictive model and stay well ahead of any issues by simply adding FC before or after an event.

There are countless times where AQR systems have been in inspect mode for who knows how long (within the six days of my team not being there) and the pool water is struggling. Not to mention water level…

I’m searching for methodology to allow me to better serve my business and pools. I’m hoping to find that in the science.

 

[IN DEPTH]

UV predominantly triggers decay of hypochlorite ion (OCl^-) into chloride Cl^-. That means all the equilibriums have to reshuffle, some HOCl turns into OCl^-, and some chlorinated Cyanurates release some chlorine into HOCl and OCl^-.

Some energy is released from the system as nitrogen and some chloride reforms with sodium to return to salt. The process repeats.

I was more interested in the photo-reactivity of the reaction. Is UV not a contributing factor? It may not be and the shielding effect is purely a positive side-effect.

 

[IN DEPTH]

I agree, However that is not the purpose of TFP. TFP teaches a method of pool care that thousands upon thousands of people have proven works.

Our purpose is NOT to teach other methods or argue about the merits of TFP.

TFP is a collection of knowledge, methods and processes that work.......time after time.

"If it ain't broke..." *

* Off the subject. but the military refined that to be, "If it ain't broke, keep on fixin' it until it is!)

(

I get that, 100%.

But the TFP method isn’t so fragile that it needs to be defended by censorship.

I’ve read the forum rules and I’ve read the TFP method. I agree with the methodology for the most part and I recommend the platform to my clients. However, I don’t see where the TFP extends to posts where I have been muted or outright deleted.

However, I’m not teaching anything when I make a post. I can’t always know what is and what is not within the TFP method, but I do what where I have been successful countless times in the field without doing harm to people or pool systems over decades.

Why have a forum of ideas where one must be careful to not post something that is judged to be not part of the TFP method?

Basically, you’d need an Ask-A-TFP-Expert system instead of an open forum.

Be careful about what you are building and defending!

 

[ajw22]

Why have a forum of ideas where one must be careful to not post something that is judged to be not part of the TFP method?

This is not a forum open to all ideas and debate.

Basically, you’d need an Ask-A-TFP-Expert system instead of an open forum.

Bingo!

This is a Forum to discuss and help each other with TFP Methods.

 

[duraleigh]

Yeah, we have only been doing this since around 2007.

We are Chevy dealers and you think we should espouse Fords and Hondas?.......not interested. sorry.