How much FC will be consumed each day during summer under AZ sun?

[jiangu1]

Hi, everyone

After following instructions from TFP, I finally have a clean nice pool with balanced water: TA 85, CH 350, CYA 45-50. My overnight FC lost is always 0 now. One thing bothers me is the consumption of the FC during the day with the AZ sun. My recent measurement showed FC loss of (11.5-6.5)=5, (6.5-2)=4.5, (9-5.5)=3.5. It seems 1 Gallon of 10% liquid chlorine (raise my pool FC 7.4 ppm) will last me 2 days. Is this normal? Anyway to reduce the FC loss during the day?

 

[mknauss]

I average about 4.5 ppm FC loss per day in June, July, and August.
Sounds pretty normal to me.

 

[Tres Gatos]

With full sun and 100+ temps in AZ I lose 1-2 ppm a day. 1 gallon lasts me about 3 days, that's normal in the summer. Also check the date born of the chlorine it's probably not close to 10% if it's older than 30 days and not stored inside.

 

[Chasarms]

My pool is fully exposed to the sun, and it is not at all uncommon for me to lose around 4 ppm on a high UV day.

 

[jiangu1]

Thanks for all your replies! It is pretty normal then. I tested today again. It is a (8-5)=3ppm. I guess if the starting FC is low, the loss will be less. Seems a lower CYA could have some advantage since it allows an overall low FC. Will test it.

 

[mknauss]

Seems a lower CYA could have some advantage since it allows an overall low FC.

Not really. If my CYA drops below 70, my FC loss goes up.

 

[sbcpool]

You will lose a lot more adding enough chlorine to last two days than you will adding less each day. The higher the FC in relation to CYA, the faster it's lost.

 

[jiangu1]

Maybe that's because you have a SWG, which needs a minimum CYA of 70? I have a non-SWG pool, and my CYA could go down to 30.

 

[jiangu1]

Last post is for mknauss. I wanted to quote the post, but it didn't work :-(.

Agree with sbcpool.

 

[jiangu1]

With full sun and 100+ temps in AZ I lose 1-2 ppm a day. 1 gallon lasts me about 3 days, that's normal in the summer. Also check the date born of the chlorine it's probably not close to 10% if it's older than 30 days and not stored inside.

Now I see by just replying a post, the post will be quoted. To "Tres Gatos", it is amazing that you can have a 1-2 ppm loss of FC. Bullhead city is as hot as Phoenix during the day, but cooler during the night. I am wondering if you have a low CYA level, or just because your water temp could be lower than here due to your cooler night? My non-SWG pool CYA is ~ 45-50.

 

[sbcpool]

My CYA is about 50 and I'm not quite as hot as Phoenix and Bullhead, but my altitude is a little higher so more UV. I lose about 2 ppm per day if I start out the day around 6. When using liquid chlorine I have to add a half-gallon of 12.5% every day.

 

[Chasarms]

Thanks for all your replies! It is pretty normal then. I tested today again. It is a (8-5)=3ppm. I guess if the starting FC is low, the loss will be less. Seems a lower CYA could have some advantage since it allows an overall low FC. Will test it.

That was not my experience. At 30, I was consistently at a 4.5-5 loss. 40-50 lowers to the 3.5-4 range.

 

[Tres Gatos]

Now I see by just replying a post, the post will be quoted. To "Tres Gatos", it is amazing that you can have a 1-2 ppm loss of FC. Bullhead city is as hot as Phoenix during the day, but cooler during the night. I am wondering if you have a low CYA level, or just because your water temp could be lower than here due to your cooler night? My non-SWG pool CYA is ~ 45-50.

The Bullhead City area is usually very windy and the evaporation will typically drop the pool temperature 7- 8 degrees overnight.

 

[jiangu1]

My CYA is about 50 and I'm not quite as hot as Phoenix and Bullhead, but my altitude is a little higher so more UV. I lose about 2 ppm per day if I start out the day around 6. When using liquid chlorine I have to add a half-gallon of 12.5% every day.

My CYA is about 50 and I'm not quite as hot as Phoenix and Bullhead, but my altitude is a little higher so more UV. I lose about 2 ppm per day if I start out the day around 6. When using liquid chlorine I have to add a half-gallon of 12.5% every day.

Thanks for sharing. I just finished the tests today. My FC last night was 5. After adding 32 oz 10% bleach, it was 6.5 this morning. And it was 5 tonight. I am getting the same range as you have. I think last time my FC dropped from 6.5 to 2 during the day could be due to the windy day with lots of leaves falling into the pool. I will see if I can maintain it this way.

 

[jiangu1]

That was not my experience. At 30, I was consistently at a 4.5-5 loss. 40-50 lowers to the 3.5-4 range.

Thanks for sharing! As mentioned above, now I feel that FC loss depends on the starting FC level in the morning and its ratio to CYA. Maybe CYA level itself is not so critical. When I have chance, I will test a low CYA level to see if it will match your experience.

 

[jiangu1]

The Bullhead City area is usually very windy and the evaporation will typically drop the pool temperature 7- 8 degrees overnight.

Thanks!

 

[Chasarms]

Thanks for sharing! As mentioned above, now I feel that FC loss depends on the starting FC level in the morning and its ratio to CYA. Maybe CYA level itself is not so critical. When I have chance, I will test a low CYA level to see if it will match your experience.

I always try to stay within the recommended targets based on the Chlorine/CYA chart.

At 30, I would raise to 6 ppm and sometimes be as low as 1 by the evening. At 40, I raise to 7 ppm and haven’t been below 3.

Although it is a moot discussion for me now since I automated the LC dosing.

 

[jiangu1]

Just want to update everyone that I have been able to add 24oz of 10% bleach each night to raise my FC from 5 to ~ 6.5-7, then drop back to 5 after a full day AZ sun. I want to be on the safe side to make sure my FC stays above 4 (my CYA 45-50, I saw my pool generated CC when FC dropped below 4). Maybe 32 oz/day is even safe to account for non-fresh bleach. But anyway, the daily FC drop due to Sun is ~ 1.5ppm. I feel I don't have to measure FC each day anymore . I can confidently add 24 oz of bleach each night and know my pool will be ok! Will test FC drop after temp drops (now my water temp is 93F). Thanks TFP and everyone's input!