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

jiangu1

Member
Jul 22, 2020
15
Phoenix, AZ
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?
 

Tres Gatos

Well-known member
Apr 13, 2019
77
Bullhead City, AZ
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.
 

jiangu1

Member
Jul 22, 2020
15
Phoenix, AZ
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.
 

sbcpool

Well-known member
Mar 10, 2015
584
Upland, CA
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

Member
Jul 22, 2020
15
Phoenix, AZ
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

Well-known member
Mar 10, 2015
584
Upland, CA
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

Silver Supporter
May 8, 2020
347
Dardenne Prairie, MO
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

Well-known member
Apr 13, 2019
77
Bullhead City, AZ
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

Member
Jul 22, 2020
15
Phoenix, AZ
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

Member
Jul 22, 2020
15
Phoenix, AZ
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.
 

Chasarms

Silver Supporter
May 8, 2020
347
Dardenne Prairie, MO
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

Member
Jul 22, 2020
15
Phoenix, AZ
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!
 
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