How much FC loss is a concern

[tedinelkgrove]

I realize my CYA is high (150ppm) and will drain pool after our guests leave. I use the pool calculator to determine how much liquid chlorine to add daily. I use a desired FC value of 15. Evey morning I test and results are ~ 11-12ppm. Is that a 3-4ppm a concisderable amount to lose, or nothing to worry about?

I can't wait to drain the pool and bring CYA down to use a lot less chlorine.

Thanks.

 

[Bama Rambler]

I usually loose 3 to 4 a day, CYA is 45. Pool is in full sun most of the day. Sun eats a lot of chlorine.

 

[johnfromphilly]

I realize my CYA is high (150ppm) and will drain pool after our guests leave. I use the pool calculator to determine how much liquid chlorine to add daily. I use a desired FC value of 15. Evey morning I test and results are ~ 11-12ppm. Is that a 3-4ppm a concisderable amount to lose, or nothing to worry about?

I can't wait to drain the pool and bring CYA down to use a lot less chlorine.

Thanks.

It is my understanding you are talking about losing the 3-4ppm overnight?? If so...

You should test at night, after the sun sets- 1 hour after lst added chlorine and turn off anything that adds chlorine (swg, chlorinator etc). Then test again in the am before the sun hits your pool. If it drops more than 1 ppm then something organic is using it up ( eg algae). This is the overnight Chlorine drop test. Don't just add the chlorine and guess at the 15ppm- test it.


Here are directions on the overnight test: http://www.troublefreepool.com/pool-school/overnight_fc_test

 

[JasonLion]

With CYA around 150, losing 3 to 4 ppm of FC means something is wrong. The most likely cause is a low level algae problem.

 

[tedinelkgrove]

Thanks for the replies. I will try the overnight chlorine drop test. I have a feeling it is fine, but want to make sure and be proactive. I test in the mroning and add chlorine then. I don't test again until next morning. Since I get full sun, I would imagine the drop is result of sun. I'll post results overnight Cl drop tomorrow.

 

[gsxr1181]

I'm dropping 3 ppm a day, and that's with a clear pool cover.

 

[chem geek]

I usually loose 3 to 4 a day, CYA is 45. Pool is in full sun most of the day. Sun eats a lot of chlorine.

You could try operating at a higher CYA level with a higher proportional FC level. Most people find that this reduces the absolute chlorine loss so in your case that might drop it to 2-3 ppm FC per day which is more typical.

 

[tedinelkgrove]

FC after dusk, 10.5
FC this morning, 10

 

[JasonLion]

The overnight test didn't show any problem with organics/algae, so maybe that is normal for your pool. With a very high CYA level, FC loss to sunlight is usually quite low. If you have a lot of people swimming every day or a few people swimming for a long time, that could contribute to your FC loss.