Too High Chlorine?

[hokiejaws07]

New pool owner and trying to gather as much advice as possible. My pool store sticks to the 1-4 level for chlorine. The owner even said the lower I can have it the better and he would not go above four.

Right now, i am using tabs (I understand the negatives of them).

My FC levels the last couple of days days have been 9, 8.5, and today, 8.

I am using the TF-Pro Test. With that much chlorine, do I necessarily have to have a tablet in the skimmer at all times or can I just average a certain amount each week. For instance, put one on Monday and another Thursday (even if I have zero in on Wednesday), as long as my levels are fine.

I just don’t want too much chlorine in my pool to harm our skin and bodies as well as the liner.

Here are all my test numbers:

FC: 8.0
pH: 7.8
TA: 150
CH: 150
CYA: 60

 

[Griswald]

FC of 8.0 is exactly what you want. An easy method is to multiply your CYA by .8, round up to the next whole number and add 2. So CYA of 60 × .8 = 4.8 or 5+2=7.0. Thats your target number, keep your FC at or slightly above 7.0 and it will not harm your skin or bodies or liner...just algae.

See, trouble free!

Oh, and pH is more damaging to skin, so keep it in the 7's.

 

[hokiejaws07]

FC of 8.0 is exactly what you want. An easy method is to multiply your CYA by .8, round up to the next whole number and add 2. So CYA of 60 × .8 = 4.8 or 5+2=7.0. Thats your target number, keep your FC at or slightly above 7.0 and it will not harm your skin or bodies or liner...just algae.

See, trouble free!

Oh, and pH is more damaging to skin, so keep it in the 7's.

For some reason I can’t keep my pH down. I’ve even poured in pH decreased.

Why would my pool store and owner be of the mindset of 1-4 chlorine level? The owner even stressed the importance of keeping it low. I also read a higher chlorine level can damage the liner?

 

[Texas Splash]

Why would my pool store and owner be of the mindset of 1-4 chlorine level? The owner even stressed the importance of keeping it low. I also read a higher chlorine level can damage the liner?

Because they really do not understand chemistry or the FC-CYA relationship. They are regurgitating decades-old "generic" recommended levels. The same people that sell you chlorine tablets will look at you with a straight face in a few months and tell you to drain your pool - because of those tablets.

TFP uses the FC/CYA Levels which maintains about a 7.5% chlorine to stabilizer ratio to ensure safe and reliable sanitation. But if you listen to the pool store techs, you'll go nuts. Also, never put tabs in the skimmer. They are too acidic for that area. Use a floater.

Be sure to always reference our Pool Care Basics page for lots of great info.

 

[hokiejaws07]

Because they really do not understand chemistry or the FC-CYA relationship. They are regurgitating decades-old "generic" recommended levels. The same people that sell you chlorine tablets will look at you with a straight face in a few months and tell you to drain your pool - because of those tablets.

TFP uses the FC/CYA Levels which maintains about a 7.5% chlorine to stabilizer ratio to ensure safe and reliable sanitation. But if you listen to the pool store techs, you'll go nuts. Also, never put tabs in the skimmer. They are too acidic for that area. Use a floater.

Be sure to always reference our Pool Care Basics page for lots of great info.

Appreciate. I am slowly converting to TFP, but have a ton of chlorine tablets to use. My CYA doesn’t seem to be going up too much at the moment.

Just worried the high chlorine can hurt us as well as the pool (again, brand new pool owner). The CDC recommends 1-3 ppm for chlorine too.

 

[ajw22]

For some reason I can’t keep my pH down. I’ve even poured in pH decreased.

Your TA of 150 is what causes your pH to rise rapidly.

In many pools pH is never stable and the TA is always pushing the pH up.

Lower Total Alkalinity

A lower Total Alkalinity level can help a pool owner stabalize their pH increase. We'll explain how to lower TA with a little help from muriatic acid.

www.troublefreepool.com

TA - Further Reading

www.troublefreepool.com

Why would my pool store and owner be of the mindset of 1-4 chlorine level? The owner even stressed the importance of keeping it low. I also read a higher chlorine level can damage the liner?

The pool store owner is correct for a pool that has 0 CYA. He does not understand the buffering that CYA does to chlorine and with CYA 60 and FC of 8 you have less then 0.1 of active HOCL.

CYA - Further Reading

www.troublefreepool.com

CYA Chlorine Relationship - Further Reading

www.troublefreepool.com

Just worried the high chlorine can hurt us as well as the pool (again, brand new pool owner). The CDC recommends 1-3 ppm for chlorine too.

The CDC also does not recognize what CYA does and talks about chlorine in pools with 0 CYA.

The pool industry is slowly coming around the how CYA changes the chlorine recommendations.

 

[hokiejaws07]

Your TA of 150 is what causes your pH to rise rapidly.

In many pools pH is never stable and the TA is always pushing the pH up.

Lower Total Alkalinity

A lower Total Alkalinity level can help a pool owner stabalize their pH increase. We'll explain how to lower TA with a little help from muriatic acid.

www.troublefreepool.com

TA - Further Reading

www.troublefreepool.com

The pool store owner is correct for a pool that has 0 CYA. He does not understand the buffering that CYA does to chlorine and with CYA 60 and FC of 8 you have less then 0.1 of active HOCL.

CYA - Further Reading

www.troublefreepool.com

CYA Chlorine Relationship - Further Reading

www.troublefreepool.com

The CDC also does not recognize what CYA does and talks about chlorine in pools with 0 CYA.

The pool industry is slowly coming around the how CYA changes the chlorine recommendations.

Thank you for the clarification. So right now, my pool is safe to swim in? The “high” chlorine levels won’t hurt us?

 

[ajw22]

Thank you for the clarification. So right now, my pool is safe to swim in? The “high” chlorine levels won’t hurt us?

With CYA 60 the pool is safe to swim in up to FC of 24 ppm. That is shown as the SLAM FC level in ...

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

The active chlorine is way less then 4 with the rest buffered as reserve chlorine with the CYA.

 

[hokiejaws07]

With CYA 60 the pool is safe to swim in up to FC of 24 ppm. That is shown as the SLAM FC level in ...

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

The active chlorine is way less then 4 with the rest buffered as reserve chlorine with the CYA.

From reading that chart, 60 CYA is as high as I want to go, right? I need to work on reducing it, it seems.

 

[ajw22]

From reading that chart, 60 CYA is as high as I want to go, right? I need to work on reducing it, it seems.

CYA 60 is as high as you want to go if chlorinating with liquid chlorine or tabs. That is why you should stop using tabs that add CYA.

At this point in the season I would not work on reducing the CYA. The CYA will naturally degrade over time and into the winter. So don't add more CYA and your CYA will slowly drop over the next few months.

Have you considered getting a SWG that will create the needed chlorine for your pool from salt?

 

[BK MAC]

Appreciate. I am slowly converting to TFP, but have a ton of chlorine tablets to use.

Sell them and set yourself free! I still have a bucket of tri-chlor tabs and di-chlor powder my pool store sold me. I'll get around to selling them at some point. In the meantime, I switched to liquid chlorine for two seasons and finally installed a SWG this year. I get it, the sting of spending money unwisely never feels good. But continuing with tri chlor tabs will only cost you more time, money and aggravation in the end. Cut your losses and make the conversion.

 

[Deb04]

Although anecdote isn’t proof, I can tell you that ive been keeping my FC at 7.5-9 for 15 summers and my liner is showing almost no signs of wear. It is way past its life expectancy of 7-10 yrs. We also have allowed our 8 yr old precious granddaughter to play, now swim, in the pool since her first full summer, which we never would have done if we has the slightest doubt about the safety.

 

[DrewLG]

So right now, my pool is safe to swim in? The “high” chlorine levels won’t hurt us?

If you have CYA in your water, the "high" free chlorine level absolutely will not hurt you.

Here's why:

The recommendation you got from the previous owner is basically what's always been recommended for commercial pools that traditionally did not use CYA. The recommendation is for very low levels of free chlorine because when you add chlorine to water without CYA, two compounds are formed in approximately equal proportions: Hypochlorous acid (HOCl, which is what does all the disinfecting and is also what irritates skin and damages equipment), and hypochlorite ions (OCl-, which doesn't do any of those things).

When you test for free chlorine in a pool without CYA, you're measuring the concentration of both compounds combined. So if you measure 4 ppm free chlorine, the water contains 2 ppm HOCl and 2 ppm OCl-. That 2 pppm HOCl is about the most you'd want to swim in; more isn't necessarily dangerous, but it would be uncomfortable and potentially damaging.

With CYA, the picture is very different.

When you add chlorine to water that contains CYA, the chlorine reacts with the water and CYA to form THREE compounds, in approximately these proportions:

2.5% HOCl
2.5% OCl-
95% stabilized chlorine

The stabilized chlorine is just chlorine held in reserve and somewhat protected from the sun: It doesn't disinfect and it doesn't burn your skin; it just slowly changes to HOCl to replace HOCl that's used up.

When you measure free chlorine in a pool with CYA, the measurement includes all three compounds, but that 2.5% HOCl is only a tiny portion of the measurement. So if you measure 4 ppm in a pool with CYA, that means there's only 0.1 ppm of HOCl in the water -- 1/20 as much as in a pool with 4 ppm FC and no CYA.

You can extrapolate and see that even with 10ppm FC -- or 16 or 20ppm or more, depending on the concentration of CYA -- the concentration of the irritating, damaging (and disinfecting) HOCl can be lower than even 1ppm FC in a pool with no CYA.

Oh, and in case you're concerned about the HOCl's ability to disinfect at such a low concentration... Even 0.05 ppm HOCl is enough to keep the water bacteria- and algae-free, so 6 ppm FC in your 60 ppm CYA pool would make twice that amount continuously available, and 10 ppm would disinfect even quicker.