Daily Chlorine Usage and FC/CYA Chart

[DanF]

Hi,

It's been about a month since I ditched tablets and pool store testing and began my own TFP-style maintenance. I have a few question about FC levels for which I search around and couldn't quite find.

My CYA is 50 (no SWCG, at least yet). According the FC/CYA chart I should be at 6-8 ppm. Let's call it 7. I have been adding 40 oz of 12.5% bleach daily for the past week and my FC readings have been steady at 5.5 ppm. I would like to raise my FC to 7. My daily dosage provides just over 3 ppm of FC. Since my FC levels have been steady, can I assume that my pool is consuming ~ 3 ppm/day?

If so, how do I go about getting the FC level to 7 ppm? Pool math says to add 19 oz of 12.5%, but I'm thinking that's just to get it 7 once, and then it will drop back to 4 after the day's usage. Do I add enough to get to 10 ppm, then revert back to the 40 oz/day to cover the daily usage?

Do the FC levels indicated in the FC/CYA chart represent levels prior to dosing with chlorine, after dosing, or somewhere in between?

Am I overthinking this? (been known to do that )

 

[IceShadow]

The levels on the chart are where you want to maintain the pool. So add enough all at once to get to the top of the recommended range each day. You don’t want it going below the minimum. Don’t bother going over the top of the recommended range - you will just burn lots more chlorine per day. 2-4ppm usage to sun is typical.

 

[Mdragger88]

Always add how much it takes to get to fc of 8 - you never wanna get to minimum on the FC/CYA LevelsThen you always have a buffer.

 

[mknauss]

Your daily use is 3 ppm FC. That is great. Raise your FC to 7 or 8 ppm. Test the next day. Your FC loss should still be right at 3 ppm. Your maintenance dose should not change.

 

[DanF]

Thanks everyone. Should I consider bumping my CYA to 60 or maybe 70, given summer is definitely here (112F yesterday) in the desert? I know a higher CYA will require higher levels of chlorine, but daily maintenance should be lower?

 

[IceShadow]

You are correct. Start with 60 for a week or so and see how it goes. I don’t go above 50 but I’m a little more northerly than you are!

 

[ajw22]

Thanks everyone. Should I consider bumping my CYA to 60 or maybe 70, given summer is definitely here (112F yesterday) in the desert? I know a higher CYA will require higher levels of chlorine, but daily maintenance should be lower?

Dont go over CYA 60 without a SWG. With higher CYA your FC target gets towards 10. Your pH test becomes inaccurate with FC above 10. CYA 50 is the sweet spot for non-SWG pools.