Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

Jump to latest Follow Reply
ionizer

ionizer

Gold Supporter
Jun 7, 2016
254
Marlboro, NJ
Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

Hi everyone. I've been following the advice here and doing my daily testing. I've passed the OCLT, but im waiting for a small leak to be repaired and as such, losing a little water everyday and having to kick up my FC about 2-3ppm every 1-2 days.

As such, I've been adding anywhere from 30-98 oz of liquid chlorine a day to keep levels at about 7-8ppm with a CYA of around 60 and CC 0-0.5.

My question is about the warnings that appear on bottles of liquid chlorine. The warnings state that you shouldn't enter the water unless the chlorine level is below 4ppm. Now, I know we adjust our levels based on the CYA in the pool, but my question is - why don't the chlorine manufacturers, who have nothing but incentive (more chlorine usage = more money) to do so, state higher PPM if CYA is accounted for?

I really am fearful that the 7-8ppm FC level I am keeping is "too high" and that it becomes more dangerous to swimmers at the level. This is purely a fear based on the fact that all labels regarding chlorine indicate 4ppm as a max before swimmers can enter. Why wouldn't the chlorine manufacturer say "you can go in at higher levels if CYA is higher?"

Also, I get that we adjust Chlorine levels for CYA because the CYA makes it less efficient - but does that mean it has a reduced impact on swimmers too? I mean it's still in the water, still going against your skin and eyes. Does the CYA make it sting less against your eyes or does it simply make it less effective for killing bacteria?

I am just a worry-wart and need some science to backup keeping my chlorine levels where they are. I get the science behind the CYA association, but still fear how that impacts humans in the water.

Help put me at ease with some science!
 
Re: Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

Yes, the higher the CYA level as you put it the less "impact" on swimmers. When my CYA was around 250 I had to keep the FC around 20.
 
Re: Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

Yes. The CYA buffers the FC. If you had a CYA of 80 and a FC of 30 and the pool was clean and clear you wouldn't be able to tell.
 
Re: Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

ionizer,

When CYA is present, roughly 95% of the FC you measure is chlorine that is chemically bound to the CYA molecule. The remaining 5% splits up into hypochlorous acid (the stuff that is good at killing algae and oxidizing bather waste) and hypochlorite ion (also a sanitizer and oxidizer, just less effective). The chlorine that is bound to the CYA gets released slowly as the HOCl/OCl- gets used up. When the chlorine is bound to the CYA molecule, it can be thought of as being "inert" or harmless. The FC you measure with your kit is the sum of all active chlorine species in the water - [HOCl] + [OCl-] + [HCy-Cl]. The actual concentrations of HOCl and OCl- in your pool water is at the parts-per-billion level.

The reason why the chemical bottles are labeled that way is for EPA regulatory compliance. The EPA assumes chlorine is added to water with NO CYA present. So, if you extrapolated TFP FC levels to zero CYA, then you wouldn't have more than 1ppm FC in the water and even at that level the FC would feel harsh.
 
Re: Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

JoyfulNoise said:
ionizer,

When CYA is present, roughly 95% of the FC you measure is chlorine that is chemically bound to the CYA molecule. The remaining 5% splits up into hypochlorous acid (the stuff that is good at killing algae and oxidizing bather waste) and hypochlorite ion (also a sanitizer and oxidizer, just less effective). The chlorine that is bound to the CYA gets released slowly as the HOCl/OCl- gets used up. When the chlorine is bound to the CYA molecule, it can be thought of as being "inert" or harmless. The FC you measure with your kit is the sum of all active chlorine species in the water - [HOCl] + [OCl-] + [HCy-Cl]. The actual concentrations of HOCl and OCl- in your pool water is at the parts-per-billion level.

The reason why the chemical bottles are labeled that way is for EPA regulatory compliance. The EPA assumes chlorine is added to water with NO CYA present. So, if you extrapolated TFP FC levels to zero CYA, then you wouldn't have more than 1ppm FC in the water and even at that level the FC would feel harsh.
Click to expand...


thanks everyone.

So you think it is just a liability issue that the bottles don't say "1-4pmm if CYA is 0" but "can be higher with a higher CYA"? I would think, if i were a manufacturer of chlorine, I would want to encourage more usage of my product and do everything legally possible to get people to use more, at safe levels.

Can you think of any reason they don't specify the disclaimer about CYA amounts and higher amounts? Any reason the EPA doesn't recognize it? Are we introducing science that the EPA disagrees with?
 
Re: Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

Manufacturers must follow EPA guidelines, and EPA guidelines have never taken in to account the effect CYA has on chlorine. Will they ever? Who knows, but there are some signs that changes are coming but will be slow and incomplete.

Here is a good illustration by chem geek showing the active chlorine levels based on FC and CYA: http://troublefreepool.com/~richardfalk/pool/HOCl.htm

If you look at that, you will see that 3 ppm FC at zero CYA (which is what the standard guidelines assume) has an active chlorine level of 1.45. If you look at the 50 CYA line you see that you need 30-40 FC to get the same active chlorine level. Using 50 (I know yours is at 60 but I don't feel like doing the math) an FC level of 10 is similar to having 0.2 FC with no CYA. So keeping your FC around 6-7 is waaaaaay less harsh on your pool, swimsuits, skin, hair, everything than a pool with no CYA and just 1 ppm of FC.

Hunt down some of chem geek's old posts, he went way in to detail about the actual chemistry and science behind what CYA does to chlorine and how the FC/CYA ratio came to be. It is an interesting read, but a bit outside my personal chemistry understanding.

EDIT: I will say that there have been times where the EPA has considered the topic. Certain industry members convinced them that there was not enough data to support it. Rather than, say, investigate it further to come to a better understanding it was simply put to bed.
 
Re: Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

As with many things, the EPA has lots of stuff on its plate. While published studies started in the 70's about the effects of CYA there has been no real reason to address the issue. Changes to policy cost money.

They don't spend money unless someone is demanding changes.

The pool chemical industry doesn't care about change, because then they would have to admit to the chemical roller coaster they put people and their pools on. Why just sell chlorine when we can have all these other neat chemicals to sell to correct "problems".

So, with all that being said, follow the money.....

People say TFP and its followers are huge, but compared to the chemical industry we are a pimple on an elephants rear end. The pool industry is hundreds of millions of dollars (billions?) and TFP wonders where we will get money to keep the lights on.....
 
Re: Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

Always keep in mind that TFP pools tend to consume less chlorine, not more.

We maintain a higher FC level, but less is consumed. This is partly due to careful management and judicial use of CYA. It is also partly due to keeping our pools cleaner. And I think it's largely due to not doing regular shocking. And finally because we don't need to drain/refill.

- - - Updated - - -

So the idea for a chem company to encourage higher FC levels to boost sales would not necessarily work well for them. For example, there would be every chance they would lose sales because of fewer people adopting the "shock weekly" approach.
 
Re: Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

The science behind chlorinated cyanurates is well over 40 years old. They were first introduced into water treatment back in the 1950's if my memory serves me correctly. Their use in swimming pools and discussions of the relevant chemistry of swimming pools using cyanurates dates as far back as the 1970's. The EPA and other regulatory agencies know of it and likely understand it well enough to a certain degree. They simply write their regulations to cover the widest margins. So since they do not stipulate the use of cyanurates at any specific levels, there's no way to account for what people would use and they're not about to write a regulation that requires an individual to solve an equilibrium chemistry problem with 9 variables and 10 simultaneous equations. So they choose to write the regulation in a way that covers all bases - 1-4ppm FC for swimming pools (full stop!). A human being can swim in water with 4ppm FC and no CYA. It won't be a pleasant swim experience but it won't kill you either.
 
Re: Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

We're a bit luckier here in Aus. The chlorinating liquid label recommends higher levels for stabilized pools. So some progress is being made :)
 

Enjoying this content?

Support TFP with a donation.

Give Support
Re: Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

JoyfulNoise said:
The science behind chlorinated cyanurates is well over 40 years old. They were first introduced into water treatment back in the 1950's if my memory serves me correctly. Their use in swimming pools and discussions of the relevant chemistry of swimming pools using cyanurates dates as far back as the 1970's. The EPA and other regulatory agencies know of it and likely understand it well enough to a certain degree. They simply write their regulations to cover the widest margins. So since they do not stipulate the use of cyanurates at any specific levels, there's no way to account for what people would use and they're not about to write a regulation that requires an individual to solve an equilibrium chemistry problem with 9 variables and 10 simultaneous equations. So they choose to write the regulation in a way that covers all bases - 1-4ppm FC for swimming pools (full stop!). A human being can swim in water with 4ppm FC and no CYA. It won't be a pleasant swim experience but it won't kill you either.
Click to expand...
That too....

I guess I have to take off my conspiracy hat.....
 
Re: Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

Sure thing... not to e interpreted as any sort of recommendation on my part!! Not sure the picture is going to work right; having trouble getting it upright. Android is in my very near future!!!
Aus Chlorine Label.jpg
 
Re: Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

In comparison, my liquid chlorine bottle says that stabilized pools need to be maintained with FC levels of between 1.0-1.5. That's all.

Here are my thoughts:

I like that they mention a specific CYA range and that it is reasonable for non-SWG pools which would be their primary customer base.

I also like that they give at least a minimum FC level.

I find it interesting that their recommendation of a minimum of 3ppm FC with a CYA of 30-50 is exactly the minimum outlined in the "best guess" chart which was the original guide for the Chlorine/CYA relationship.

I like that they talk about testing and reagents.

They also strongly caution against CYA over 100, and even warn against 50 at their minimum FC level.

It's not exactly TFP guidelines, but it's progress! WOW!!
 
Re: Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

So not to get political, hailing originally from Canukistan, but SEE, it IS possible to do things differently... ;)

I honestly suspect the difference is the lobby power in the US - not any practical considerations on the part of the EPA. Human health seems to get trumped a lot in favor of industry status quo in this neck o' the global woods.

I will now set down my tinfoil hat and resume other activities ;)
 
Re: Question about Chlorine levels based on CYA and "Recommended 4ppm guidelines"

Yeh, it's quite different down here with respect to CYA vs. what I hear from there. Although pool stores seem just the same and say 100 is no big deal, so they're playing that same game. When I first read that label, after reading lots here, it seemed that TFP would all fit well. The only thing I'd mention for clarity is that SWG is pretty dominant here. When we looked at houses to buy, I looked at around 30 pools and only two of those were non-SWG. I have a mate who's a poolie and he said he didn't know market stats or anything, but maybe 80/90% salt.
 

Enjoying this content?

Support TFP with a donation.

Give Support
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply