Is there a consensus on how many hours is "very high levels of direct sunlight"?

[brauh01]

Is there a consensus on how many hours is "very high levels of direct sunlight"?

Good Morning!

So after spending the last two years bringing my CYA level down from the obscene levels, having been "pool stored", I've successfully lowered it to about 40 this season. In the CYA section of the ABCs of Pool Water Chemistry, it states "If you don't have a SWG or problems from extremely high amounts of sunlight, CYA is typically kept between 30 and 50. If you have a SWG or very high levels of direct sunlight, CYA is typically kept between 70 and 80." Right now I have almost 10 hours of direct sunlight, even longer in July. I am wondering if I should slowly raise my CYA back up to 70. For this season, a daily liquid bleach (12.5%) add for me has been circa 10 cups. I've been targeting FC of 8, rather than 5, as I've found that 5 would lower too quickly for me on the following day, I would have some CC and would then have to shock. (Happened twice this summer, if that information is helpful.)

By no means an urgent question, but given the global nature of this site, I'm not sure if my hours of direct sunlight are high enough to warrant adjusting my CYA target.

Thanks for all the help!

Bill

 

[pabeader]

Re: Is there a consensus on how many hours is "very high levels of direct sunlight"?

The easy answer is, "your pool will tell you"
'Normal' FC loss during the day is usually given as 3-4ppm. If you are losing more than that you probably need to bump up the CYA a little. Especially if your overnight loss is almost 0.
Usually, I see a bump of 10ppm at a time is what is suggested. This adjustment can take a little time because you have to wait between addition to be able to test for it. But the effect on the FC loss should be noticeable. Keep in mind that the variable nature of sun time will have an effect on the FC loss also. That's what makes this adjustment such a pain.

 

[Divin Dave]

Re: Is there a consensus on how many hours is "very high levels of direct sunlight"?

Hi Braugh,

TFP is all about learning how to care for a pool and all of the variances that factor in to it. The recommendations are just that. Recommendations. Intended for someone who knows nothing about pool chemistry or how to care for a pool.

All of us were at the starting line at some point. And all or most all of us as we learn, make our own adjustments to the recommended levels. The key is knowledge.

It seems you are well past the starting line. You know the issues with high CYA and what not to exceed, so, go ahead and make your adjustment to the CYA and lower the consumption of chlorine and save a few $ in the process. Nothing at all wrong with that. One note, is that if you get lazy on your chlorine additions and let some algae take hold, it will take more bleach to SLAM it. Thats the only downside.

Hope this helps,

 

[chem geek]

Re: Is there a consensus on how many hours is "very high levels of direct sunlight"?

"Normal" FC usage varies by pool. I'd say that most pools are in the 2-3 ppm FC range if people are keeping their FC/CYA levels near the minimum, but in areas in southern latitudes with normally clear skies and full sun (no shade) then pools have higher chlorine usage and are in the 3-4 ppm FC range unless they operate at a higher CYA level (i.e. 80 ppm instead of 50 ppm). Arizona and Texas tend to have the highest usage. Florida is next but they typically get enough daily cloudy skies (often with rain) that it's not as bad. Southern California can also be on the higher side, but not as much as Arizona and Texas (by Texas I mean mid to south so Houston and San Antonio, not so much Dallas and Amarillo).

Water temperature also plays a role since some chlorine loss is from chlorine oxidizing CYA, pool covers, and organics that get into the pool. So here again Arizona tends to have some of the highest usage because the pool water is often quite warm. Pools with more debris tend to have higher usage as well.

 

[brauh01]

Re: Is there a consensus on how many hours is "very high levels of direct sunlight"?

Thanks for all the responses. Using The Pool Calculaor, which I always use, and assuming the FC levels are ppm, then it looks like my usage/dosing is spot on at around 3ppm per day. I think I will not tempt fate and will continue doing what I'm doing. Thanks again!
Bill

 

[pabeader]

Re: Is there a consensus on how many hours is "very high levels of direct sunlight"?

you need to switch from the "pool calculator" over to Pool Math. I'm reading that pool calculator is not being updated or maintained.

 

[JoyfulNoise]

Re: Is there a consensus on how many hours is "very high levels of direct sunlight"?

"Normal" FC usage varies by pool. I'd say that most pools are in the 2-3 ppm FC range if people are keeping their FC/CYA levels near the minimum, but in areas in southern latitudes with normally clear skies and full sun (no shade) then pools have higher chlorine usage and are in the 3-4 ppm FC range unless they operate at a higher CYA level (i.e. 80 ppm instead of 50 ppm). Arizona and Texas tend to have the highest usage. Florida is next but they typically get enough daily cloudy skies (often with rain) that it's not as bad. Southern California can also be on the higher side, but not as much as Arizona and Texas (by Texas I mean mid to south so Houston and San Antonio, not so much Dallas and Amarillo).

Water temperature also plays a role since some chlorine loss is from chlorine oxidizing CYA, pool covers, and organics that get into the pool. So here again Arizona tends to have some of the highest usage because the pool water is often quite warm. Pools with more debris tend to have higher usage as well.

Hey, stop beating up on Arizona We like our sunshine and 360 days of clear skies just fine, thank you very much

(But you are quite right, we do consume A LOT of FC here. I'd go crazy if I didn't have my SWG!!)


Sent from my iPhone using Tapatalk

 

[jblizzle]

Re: Is there a consensus on how many hours is "very high levels of direct sunlight"?

There would be no issue bumping the CYA up to 50ppm. Also do not raise too much above the minimum FC level. The higher the FC level, the more ppm you will lose.

 

[brauh01]

Re: Is there a consensus on how many hours is "very high levels of direct sunlight"?

Thanks Pabeader!
You are absolutely correct. I downloaded the page last year and use it locally rather than on the Internet. (My signature even points to the correct version.) I know there's a bad site floating around, can't find the url at the moment. Still, I need to update to the version that has the 2015 copyright.
Thanks again.

- - - Updated - - -

Thanks jblizzle. Always something new to learn. I would guess this is why the "target" levels seem close to the "minimum" on the CYA chart (?). Bill

 

[chem geek]

Re: Is there a consensus on how many hours is "very high levels of direct ..."

I would guess this is why the "target" levels seem close to the "minimum" on the CYA chart (?). Bill

The Target levels are a bit pointless to put into a chart. The real rule is to have as your target for raising the FC when you add chlorine to be WHATEVER IS NECESSARY so that you don't go below the minimum FC/CYA by the time you next dose the pool.

 

[duraleigh]

Re: Is there a consensus on how many hours is "very high levels of direct sunlight"?

I just saw this thread. "

If you don't have a SWG or problems from extremely high amounts of sunlight, CYA is typically kept between 30 and 50. If you have a SWG or very high levels of direct sunlight, CYA is typically kept between 70 and 80."

I am not comfortable with that wording in Pool School and propose to change it. I do not believe it is wise to run a manually chlorinated pool over 50 ppm. The savings get really small and the potential problems get much larger.

 

[ping]

Re: Is there a consensus on how many hours is "very high levels of direct sunlight"?

I just saw this thread. " I am not comfortable with that wording in Pool School and propose to change it. I do not believe it is wise to run a manually chlorinated pool over 50 ppm. The savings get really small and the potential problems get much larger.

I agree with you Dave and maybe it should be the following:

Cyanuric acid, often called stabilizer or conditioner, both protects FC from sunlight and lowers the effective strength of the FC (by holding some of the FC in reserve). The higher your CYA level, the more FC you need to use to get the same effect. It is important to know your CYA level so you can figure out what FC level to aim for. CYA is typically kept between 30 and 50 for manually dosed pools and between 70 and 80 for SWG pools.

 

[chem geek]

Re: Is there a consensus on how many hours is "very high levels of direct sunlight"?

The rough difference in chlorine usage between having the CYA at 80 ppm vs. 50 ppm is roughly 25% (based on the estimates in this post). So that is the savings in chlorine that is to be traded off against the increased risk of having a more difficult SLAM at 80 ppm requiring 60% higher FC level than at 50 ppm. The savings in chlorine is like the difference between using 4 ppm FC per day at 50 ppm vs. 3 ppm FC per day at 80 ppm. Or the difference between using 3 ppm FC per day at 50 ppm vs. 2.2 ppm FC per day at 80 ppm.