HOCL residual

[xDom]

Depends how you chlorinate the pool.

What Are My Ideal Pool Levels?

Use our tool to find ideal chemical levels for any swimming pool. Check TFP recommended levels on pH, free chlorine, cyanuric acid, and more.

www.troublefreepool.com

What Are My Ideal Pool Levels?

Use our tool to find ideal chemical levels for any swimming pool. Check TFP recommended levels on pH, free chlorine, cyanuric acid, and more.

www.troublefreepool.com

CYA of 70-80 ppm?! whoah! I thought 30ppm is what I should be going for.

I saw a graph that shows the length of protection vs the ppm of CYA.
After 1 hour at 20 ppm there was 95% of chlorine remaining, at 30 ppm there was 98% and at 50 ppm there was 99%.

So increasing levels from 30% didn't offer much more protection?
There must be something I'm missing!?

 

[mgtfp]

So what CYA do you feel is ideal? 20-30 ppm?
I was reading in Falk's paper that even indoor pools should have CYA, to moderate the amount of HOCL.

That's one of the bits where it's important to go through the complete Chem Geek water chemistry thread, and not stop too early.

With an SWG it makes sense to have CYA a bit higher. Later in the thread you'll find Richard mentioning that there seems to be more UV protection at higher CYA levels than one would expect simply by the percentage of FC that's bound to CYA. This gets supported by testing that mas985 has done over the years (some of them quite recently).

That means that at the same FC/CYA ratio, chlorine decays slower under UV at higher CYA levels. This effect is always there and independent from the presence of an SWG.

You now have to balance the benefits of higher CYA against the risks. The risk is that, should your FC ever slip below the min, you might have to SLAM the pool to clear a green pool.

With a liquid chlorine pool, that risk is quite real, and you want to maintain a CYA level that allows SLAMing with reasonable FC levels. CYA 30-50 seems to be a good compromise there.

With an SWG the risk of slipping below min is much smaller. That allows harvesting the benefits of higher CYA levels. CYA 60-80 seems to work well there. More towards 80 in hot and sunny climates, more towards 60-70 in more moderate climates.

There seems to be another benifit of higher CYA with SWGs by providing the small but constantly produced chlorine amounts more efficient protection from UV, which allows running the SWG less frequent and/or on a lower setting which extends the cell's lifetime.

I get my CYA up to about 70-80 in summer. Over winter, I let it drop down to about 40. Then I keep adding again to maintain CYA 40 over the rest of winter. I prefer to maintain my CYA in the measurable area above 30 so that I know where I am, rather than turning blind below 30. In spring I first increase it to about 60, and in December I'll bump it up to 70-80. That usually gets me through summer without having to add any more.

 

[PoolStored]

The higher the CYA, the higher the FC level you need BUT the lower the FC you need to add each day. So in the long run, the cell lasts longer with higher CYA.

CYA vs UV Chlorine Loss Test Update​

Many years ago, I did a test of chlorine loss vs CYA level and published the results here: CYA Testing Update There were a few issues with the test that I wanted to resolve with some additional testing but never got around to doing it...until now...

www.troublefreepool.com

 

[xDom]

That's one of the bits where it's important to go through the complete Chem Geek water chemistry thread, and not stop too early.

With an SWG it makes sense to have CYA a bit higher. Later in the thread you'll find Richard mentioning that there seems to be more UV protection at higher CYA levels than one would expect simply by the percentage of FC that's bound to CYA. This gets supported by testing that mas985 has done over the years (some of them quite recently).

That means that at the same FC/CYA ratio, chlorine decays slower under UV at higher CYA levels. This effect is always there and independent from the presence of an SWG.

You now have to balance the benefits of higher CYA against the risks. The risk is that, should your FC ever slip below the min, you might have to SLAM the pool to clear a green pool.

With a liquid chlorine pool, that risk is quite real, and you want to maintain a CYA level that allows SLAMing with reasonable FC levels. CYA 30-50 seems to be a good compromise there.

With an SWG the risk of slipping below min is much smaller. That allows harvesting the benefits of higher CYA levels. CYA 60-80 seems to work well there. More towards 80 in hot and sunny climates, more towards 60-70 in more moderate climates.

There seems to be another benifit of higher CYA with SWGs by providing the small but constantly produced chlorine amounts more efficient protection from UV, which allows running the SWG less frequent and/or on a lower setting which extends the cell's lifetime.

I get my CYA up to about 70-80 in summer. Over winter, I let it drop down to about 40. Then I keep adding again to maintain CYA 40 over the rest of winter. I prefer to maintain my CYA in the measurable area above 30 so that I know where I am, rather than turning blind below 30. In spring I first increase it to about 60, and in December I'll bump it up to 70-80. That usually gets me through summer without having to add any more.

Thanks,
this is a bit of an eye opener for me.
I see you use the Clear Choice kits, that's what I have myself. The CYA test is a bit subjective, depends on how good your eyes are?
Like you say though, its probably easier at the higher levels.

 

[mgtfp]

Thanks,
this is a bit of an eye opener for me.
I see you use the Clear Choice kits, that's what I have myself. The CYA test is a bit subjective, depends on how good your eyes are?
Like you say though, its probably easier at the higher levels.

Yeah, takes some getting used to.

I ordered a big bottle of Taylor's R-0013 on Amazon. That allowed me to play around with the test until I felt confident. Much cheaper in the larger quantities and that's the reagent that probably lasts longest.

When I first increased my CYA up to 80, I did it in 10ppm steps, which allowed me to train myself to see these differences in the test.

No need to bump it up before winter, it's a spring/summer project.

 

[xDom]

Yeah, takes some getting used to.

I ordered a big bottle of Taylor's R-0013 on Amazon. That allowed me to play around with the test until I felt confident. Much cheaper in the larger quantities and that's the reagent that probably lasts longest.

When I first increased my CYA up to 80, I did it in 10ppm steps, which allowed me to train myself to see these differences in the test.

No need to bump it up before winter, it's a spring/summer project.

What FC to CYA do you go for? Orenda say 7.5% but I read somewhere that 5% is OK?

 

[PoolStored]

What FC to CYA do you go for? Orenda say 7.5% but I read somewhere that 5% is OK?

Stick with 7.5%. Better yet, use this:

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

For 70 CYA, result is minimum(for SWCG) of 5 and target of 8-10. I run between 9-10. Why? I can have FC demand of up to 4.5 in June/July, with sun and swimmers. 9.5 FC - 4.5 (demand) = 5.5, which keeps me above minimum.

 

[mgtfp]

What FC to CYA do you go for? Orenda say 7.5% but I read somewhere that 5% is OK?

I usually keep FC between 8-10 with CYA up to 80. It just gives me a bit of buffer time before things turn pear shaped. Like in spring when you have to gradually ramp up the SWG. Or down here in Melbourne with its four seasons in one day. You have cold cloudy weather for weeks, then you suddenly get a few 40+ days in a row with lots of UV. Being a bit higher in FC lets me just sit out those few days of higher chlorine demand before we return to the usual drizzle without constantly having to fiddle with the SWG settings. I also have a pH-meter, so I don't worry about not being able to test pH above FC 10.

I see the 5% more as the safe worst case scenario, but I wouldn't want to permanently maintain this. That would just require too much micromanaging.

Keep in mind that any FC up to SLAM is safe to swim in. Dial your SWG in so that you don't fall below your personal min FC in hot sunny summer weather, and accept that FC shoots up a bit when it's cloudy. Adjust a little over the seasons.

 

[Orion7319]

That's one of the bits where it's important to go through the complete Chem Geek water chemistry thread, and not stop too early.

With an SWG it makes sense to have CYA a bit higher. Later in the thread you'll find Richard mentioning that there seems to be more UV protection at higher CYA levels than one would expect simply by the percentage of FC that's bound to CYA. This gets supported by testing that mas985 has done over the years (some of them quite recently).

That means that at the same FC/CYA ratio, chlorine decays slower under UV at higher CYA levels. This effect is always there and independent from the presence of an SWG.

You now have to balance the benefits of higher CYA against the risks. The risk is that, should your FC ever slip below the min, you might have to SLAM the pool to clear a green pool.

With a liquid chlorine pool, that risk is quite real, and you want to maintain a CYA level that allows SLAMing with reasonable FC levels. CYA 30-50 seems to be a good compromise there.

With an SWG the risk of slipping below min is much smaller. That allows harvesting the benefits of higher CYA levels. CYA 60-80 seems to work well there. More towards 80 in hot and sunny climates, more towards 60-70 in more moderate climates.

There seems to be another benifit of higher CYA with SWGs by providing the small but constantly produced chlorine amounts more efficient protection from UV, which allows running the SWG less frequent and/or on a lower setting which extends the cell's lifetime.

I get my CYA up to about 70-80 in summer. Over winter, I let it drop down to about 40. Then I keep adding again to maintain CYA 40 over the rest of winter. I prefer to maintain my CYA in the measurable area above 30 so that I know where I am, rather than turning blind below 30. In spring I first increase it to about 60, and in December I'll bump it up to 70-80. That usually gets me through summer without having to add any more.

I’ve been running my pump and SWG 24/7, and I keep my CYA around 50-60. I’m finding that things seem to start to behave a just a bit differently when you’re building up more of a chlorine reserve during the night.

Also, you explain complex processes in a very easy to understand way. Enjoyable thread, Thanks!

 

[AUSpool]

CYA of 70-80 ppm?! whoah! I thought 30ppm is what I should be going for.

I saw a graph that shows the length of protection vs the ppm of CYA.
After 1 hour at 20 ppm there was 95% of chlorine remaining, at 30 ppm there was 98% and at 50 ppm there was 99%.

So increasing levels from 30% didn't offer much more protection?
There must be something I'm missing!?

G’day Dom, welcome to TFP.

I cant offer much more then @mgtfp and others have already offered.

If you follow our pool shop advice they ‘should’ tell you that a CyA of 30ppm is the minimum where you should be topping up to 50ppm. In Australia we actually have an Australian Standard for water quality in domestic pools, AS3633-1989. Its old but still current. Unfortunately the recommended levels that are used nowadays have been replaced by various industry standards.

From table3.2 in AS3633 when CyA is used the FC should be a minimum of 3ppm, thats greater then 3ppm. CyA is given as 30 - 50ppm and although no ratio is given, at 50ppm CyA the minimum ratio is 6 which is a bit low for me, particularly when I target a pH around 7.8. At FC 3ppm and 30ppm CyA the ratio is 10 - much better.

There is graph in a recent article by Pickens that is easy to interpret that there is little benifit from increasing CyA above 50ppm but this is theoretical, a mathematical interpretation that goes back to what data is used an how it is presented. In real life it makes a big difference but few have ever really tested it. I did, in a pool with no significant change over a week other than increasing CyA from 50ppm to 70ppm my FC increased by over 1ppm.

On a side note be cautious of the fancy new day spa salts on offer. No one has agreed on a safe or appropriate magnesium level and often you will hear them say “as per the Australian Standard” but there are no references to magnesium in the Australian Standard.

 

[mgtfp]

In Australia we actually have an Australian Standard for water quality in domestic pools, AS3633-1989. Its old but still current. Unfortunately the recommended levels that are used nowadays have been replaced by various industry standards.

Interesting, I wasn't aware of that. Just tried to find it online, but there only seem to be downloads for purchase available. But on standards.org.au I found the information "Status: Pending Revision" and "Withdrawn: 2016". So, I might hold off buying this document. But I haven't got much hope that a new revision would be released anytime soon if it's already pending since 2016.

 

[AUSpool]

Interesting, I wasn't aware of that. Just tried to find it online, but there only seem to be downloads for purchase available. But on standards.org.au I found the information "Status: Pending Revision" and "Withdrawn: 2016". So, I might hold off buying this document. But I haven't got much hope that a new revision would be released anytime soon if it's already pending since 2016.

I had no idea either until a random comment “as per the Australian Standard” got me intrigued and on the hunt. What’s interesting is that as far as FC and CyA go, an almost 35 year old standard is closer to what TFP recommends then any LPS’s or industry recommendations. I bought it but think it should be made publicly available. The issue I see with them going forward is who the stakeholders will be and what they will want in the new standard. We, the owners of the domestic pools are not well represented and while many of use release pool water to the environment via storm water, the EPA is not represented. - It would be interesting to hear their thoughts on releasing copper to the environment.

 

[mgtfp]

What's particularly interesting is that this table only specifies a min FC level, and no max value. Indeed much closer to TFP than anything any pool store has ever advised to anyone.

 

[xDom]

I usually keep FC between 8-10 with CYA up to 80. It just gives me a bit of buffer time before things turn pear shaped. Like in spring when you have to gradually ramp up the SWG. Or down here in Melbourne with its four seasons in one day. You have cold cloudy weather for weeks, then you suddenly get a few 40+ days in a row with lots of UV. Being a bit higher in FC lets me just sit out those few days of higher chlorine demand before we return to the usual drizzle without constantly having to fiddle with the SWG settings. I also have a pH-meter, so I don't worry about not being able to test pH above FC 10.

I see the 5% more as the safe worst case scenario, but I wouldn't want to permanently maintain this. That would just require too much micromanaging.

Keep in mind that any FC up to SLAM is safe to swim in. Dial your SWG in so that you don't fall below your personal min FC in hot sunny summer weather, and accept that FC shoots up a bit when it's cloudy. Adjust a little over the seasons.

Over a typical Melbourne Summer how much would you expect to see your FC drop daily? On average?

 

[xDom]

What's particularly interesting is that this table only specifies a min FC level, and no max value. Indeed much closer to TFP than anything any pool store has ever advised to anyone.

Also, I just noticed in your pic you seem to be using the magnetic stirrer from Clear Choice? They are out of stock at the moment but I was thinking of getting one. Do you recommend?

 

[mgtfp]

Over a typical Melbourne Summer how much would you expect to see your FC drop daily? On average?

Maybe 3ppm per day. Sometimes 4ppm.

 

[mgtfp]

Also, I just noticed in your pic you seem to be using the magnetic stirrer from Clear Choice? They are out of stock at the moment but I was thinking of getting one. Do you recommend?

I highly recommend it. Makes testing so much easier and more reproducible.

 

[AUSpool]

Over a typical Melbourne Summer how much would you expect to see your FC drop daily? On average?

When your FC demand is balanced with your SWG’s output you don’t really see a daily drop in FC. We measure the difference in the balance and then adjust the SWG accordingly.

 

[mgtfp]

When your FC demand is balanced with your SWG’s output you don’t really see a daily drop in FC. We measure the difference in the balance and then adjust the SWG accordingly.

That's it.

 

[xDom]

When your FC demand is balanced with your SWG’s output you don’t really see a daily drop in FC. We measure the difference in the balance and then adjust the SWG accordingly.

I know what you mean. I guess a better way of wording it would be “ how many ppm’s of chlorine a day would be consumed/depleted “