What level should I try to achieve on CYA?

[CelticDaddio]

According to the "Best Guess" chart the FC level should be within a certain range based on the level of CYA. What level should I try to achieve on CYA?

Does it really matter what my CYA level is, as long as I match the correct FC level to it?

Ed

[waterbear]

The recommended range is 30-50 ppm for most people. SWGs require a higher level (but not a higher FC level usually), and some people in very hot, sunny climates run it a bit higher with a higher FC level to minimize chlorine loss from the sun.

Edit: I'd start at the 30-50 ppm level and see how it goes. You can always bump it up a bit if you need to. If you have a SWG then run it at the high end of the manufacturer's recommendation.

[Jeffski]

Why do SWG's require a higher level and what is that optimum level?

My CYA is 30 and I was happy with that but I do have a SWG.

[chem geek]

The level of CYA recommended by different manufacturers of SWG varies by manufacturer, but some recommend 70-80 ppm (saying "80 is best"). We don't know for certain why this is. This thread (http://www.poolforum.com/pf2/showthread.php?t=4495) debates this topic but essentially we have two theories and don't know which is true (or which is the predominant factor if both are true):

1) Higher CYA protects chlorine longer and the manufacturers want users to run their SWG cells with less "on" time to maximize cell life and to reduce the rise in pH (from the hydrogen gas bubbles that cause aeration).

2) Higher CYA levels combine with the chlorine that is produced in the SWG cell thereby allowing more to be generated before saturating the cell with disinfecting chlorine. This increases cell efficiency.

Richard

[waterbear]

From the replies I have gotten when I have talked to tech support at Goldline controls I am leaning towared #2. They have not come out and said this but their explanation is more in line with this than with #1.