cya with swg and automatic safety cover

[t6pool]

Hi All,
My pool is covered most of the day and night with a coverstar auto cover. So, the pool is covered about 80% of the time when it's not in use. It gets most activity after I get home from work and during the weekends with some light weekday acitivity.

I'm running my SWG @ about 25% to maintain FC around 4.5-5 with CYA ~48. I keep my water temp ~90F. I tested for CC a few days back and got 0. I ready my taylor test kit manual the other day and saw something about the efficacy of CYA > 50 being marginal. I then read recommended CYA levels from the CYA chart w.r.t SWG's. So, now I'm at a point where I'm a little confused where the CYA should be w.r.t all of the other factors in my pool. I also wonder what I should be doing with my SWG and my pump......

One thing about the auto cover is that it is deck mounted and tends to take some debris into the pool every time I open/close it so the leaves may be taking up some FC...

The rest of the water balance looks great w/ my k-2006 and the water is sparkling clear with BBB + SWG. Thanks to all of you for posting such great info on this site. It has really helped me learn about the quality of my water along with saving tons of $$ at the pool store.

Thanks!

 

[JasonLion]

The ideal CYA level with a SWG is around 70 to 80.

There is a lot of misleading information about CYA floating around. Companies that sell trichlor tend to say that CYA doesn't matter, while companies that sell cal-hypo tend to say that CYA is terrible. Both of those groups are putting out misleading information, since CYA does matter and has both advantages and disadvantages.

 

[t6pool]

I'm still a bit confused.

If CYA is there to prevent burnoff of FC from UV rays and an unstabilized pool can burn off 1/2 of it's FC in 2 hrs
Then if my pool is covered most of the time along with the SWG running continuously at 25%,
shouldnt this reduce the need for CYA and hence allow me to run at a lower FC, therefore lengthening the life of my SWG cell by not running it at a higher amperage?

Maybe I'm really confused

Thanks

 

[JasonLion]

If the pool is exposed to the sun at all, then: having more CYA reduces the amount of chlorine you need in total and increases the lifetime of the SWG cell. I know that it is a little counter intuitive. The more CYA you have the more protected from sunlight you are. You also need to increase the FC level to compensate for the increased buffering the CYA is doing. But the increased protection from sunlight more then compensates for the increased FC level, meaning you lose less total chlorine to sunlight at higher CYA levels.

Having the pool covered will usually reduce the amount of chlorine lost to sunlight, though some covers allow UV through and don't really reduce chlorine loss very much. If your cover does reduce the amount of chlorine lost to sunlight and you use it a lot, you need to watch the FC level and not let it go to high when the pool is covered and not let it go too low when the pool is exposed to sunlight.