Two questions: CSI vs pH, and CYA levels

[Soupy]

Numbers:
pH 7.8
TA 80
CYA 22
CH 250
Salt - Can't be much
Borates 15
Temp 60 F

Question the first: At the above levels, I get a CSI of -.01. When I add acid and drop the pH back down to 7.4, CSI drops to -.39. Would it be better to maintain pH between 7.6 and 8.0 rather than 7.4 to 7.8 at this point in the season? Once it's time to swim and the water is around 80 F, this is a moot question, as 7.4-7.8 pH has CSI nicely centered around 0.

Question the second: Is there a guidline for determining the optimum CYA level for a pool? My pool gets a lot of shade, with very tall trees south of it. Almost no sun this time of year, and only a few hours of full sun even during the peak of summer. So why not run a lower CYA level? Can I just run a daytime FC loss test and use that to figure an optimal CYA level for my pool? This is my third year owning the pool and my first full season pool-store free; dropped that habit mid-summer last year. So I'm still figuring out how to best tailor standard advice to my pool.

Thanks.

 

[duraleigh]

So why not run a lower CYA level?

No reason at all. You describe a condition that gets noticeably less sunlight than other pools so you simply don't need the protection from the sun that other pools do. 30 would be my best guess as a good place to start.....How did you get a test result of 22? Interpolate?

I am not a fan of csi so have no opinion on it.

 

[Soupy]

CYA test was between 20 and 30, eyeballed it to 22. I don't think the test is that precise, but I figure I may as well log what I see.

 

[duraleigh]

Yep, many report it just like that. The test itself Is usually somehwere around +/- 10ppm but I like to think I have done it enough to be a LITTLE more accurate than that but probably not....at least in the higher ranges. :lol:

 

[JasonLion]

You don't really want CSI exactly centered around zero, it is better to have it just slightly negative. There are a couple of reasons for this, briefly PH tends to go up, not down, so counting the rare occasions when you let the PH go up a little to long biases the actual range the pool experiences. Also, the CSI inside the heater is higher which also biases the range you want to be in.