# Thread: If CYA is 40, optimal FC level is 4 - what rate will it fall

1. ## If CYA is 40, optimal FC level is 4 - what rate will it fall

If CYA is 40, optimal FC level is 4 -

What rate should the FC level fall by in 24 hours that is in an acceptable level of decline?

2. ## Re: If CYA is 40, optimal FC level is 4 - what rate will it

Depends on the level of sun intensity. Why?

Although 4ppm is not optimal, it is the MINIMUM the FC should ever be.

3. ## Re: If CYA is 40, optimal FC level is 4 - what rate will it

I was reading the CYA/FC chart, and it says minimum is 3, target is 5, so that is where i got 4 from
should by FC really be 5 if my CYA is 40?

PS: on recommended levels page it says my CYA for plaster pool to be 30-50 .. if thats true then my FC should be 5/6 at optimal?
PPS: I am using dichlor to achieve CYA level, since they haven't got a **** clue in Serbia or Hungary what a stabilizer is... (NOTE: They dont even have test kits which can measure CYA, CH, CC, ALK - so i had to order the taylor k2006 from the USA)

4. ## Re: If CYA is 40, optimal FC level is 4 - what rate will it

As noted in the Chlorine / CYA Chart, the minimum FC is 3 ppm when the CYA is 40 ppm. That would be the lowest level just before you added more chlorine. This post shows some typical average loss though it really depends a lot on the amount of sunlight. With 40 ppm CYA, you might lose around half your FC over the day so since you want the minimum to be 3 ppm, you'd have to add chlorine to get to 6 ppm. If you find that your loss is in fact this high, you might consider having a higher CYA level such as 60 ppm. At 60 ppm the minimum FC is 5 ppm but the loss may be only 30-35% so you'd have to raise your FC to around 7.5 ppm so you'd only lose 2.5 ppm FC per day instead of 3 ppm FC per day if you were at 40 ppm. At 80 ppm, the minimum FC is 6 ppm but the loss may only be 22% so you'd raise your FC to around 8 ppm so would only lose 2 ppm FC per day, but having the CYA at 80 ppm is risky if anything goes wrong since the shock FC level is rather high.

You should experiment and see your actual loss rate and just add enough chlorine so that you don't go below the minimum.

5. ## Re: If CYA is 40, optimal FC level is 4 - what rate will it

Thanks, the pool is in sunlight all day long, from the minute the sun rises until sunset due to how its positioned on our property.
I will experiment

6. ## Re: If CYA is 40, optimal FC level is 4 - what rate will it

Sorry I recalled the chart incorrectly about the 3 vs 4 being the minimum. Although chem geek has you covered.

7. ## Re: If CYA is 40, optimal FC level is 4 - what rate will it

I hope this is not a hijack of the OP, but I think it is very similar question...

I am estimating my CYA around 30 or so in my Fiberglass Pool. For some reason I am freaked about run away CYA, so I am being very careful before I rise the level.
I am in sun nearly all day, but OHIO sun not TEXAS sun...I have been tracking my usage pretty tightly.

I go from a level of 4 FC to about 2.5 consistently every day.

If I understand Chem Geeks detailed chart mentioned above, it is true that I would be better off increasing my CYA to say 50 ?

8. ## Re: If CYA is 40, optimal FC level is 4 - what rate will it

Probably ... try 40ppm and see what happens ... although a 1.5ppm loss per day is on the low side already.

9. ## Re: If CYA is 40, optimal FC level is 4 - what rate will it

Yeah, you are already at a rather low loss rate. Though increasing the CYA and FC proportionately may lower that somewhat, the savings won't be that much since you are already at a low level. You can try and see, but personally I doubt it will be worth it.

10. ## Re: If CYA is 40, optimal FC level is 4 - what rate will it

thanks gang...since I already have the CYA chems to increase a bit, and since summer is not fully upon us yet, I am thinking I will take her up to 40 and then continue to monitor closely, etc.

11. ## Re: If CYA is 40, optimal FC level is 4 - what rate will it

Originally Posted by toofast
thanks gang...since I already have the CYA chems to increase a bit, and since summer is not fully upon us yet, I am thinking I will take her up to 40 and then continue to monitor closely, etc.
lmk how u do at 40, im curious as to your loss patterns
cheers

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