gucu said:
FC drop was less than 1ppm last night and CC seems to be at or below .5ppm. Going to keep it up 1 more day to be sure.
A few questions: Will the CC readings change due to the time of day or temperature?
Also, when doing the FAS-DPD test the kit says to use a heaping spoonful of the powder. How critical is the amount of powder used? I like to be exact for consistency and this is a somewhat loose measurement.
I am going to target my CYA at 40 which will require a 3-7 on FC levels. Does this require me to use the FAS-DPD test every day instead of the basic test due to the higher FC levels? Or should I keep the CYA lower?
If CCs are 0.5 or less consistently, consider them at 0. There will always be CCs in the pool if you have people in the pool. CC stands for combined chlorine, which is another word for chloramines. Chloramines are the byproduct of Free Chlorine oxidizing bather waste (specifically Nitrogen compounds like sweat, pee, spit, sunscreen). In an otherwise clean pool, the CCs will disappear quickly because they are either broken up by the sun/UV rays or further oxidized by more chlorine. For us, .5 CC = 0 CC.
For normal maintenance levels, if you put in a heaping spoonful, and it turns pink, you're fine. If it flashing pink and goes back to clear, you need more. The only time you really need to worry about not putting in enough is if you're in the middle of the SLAM process.
Your last question is a great question because it means you are 100% in tune with your pool's chemistry. The level you maintain for CYA will vary by pool size/surface area and sunlight. I like to run mine up between 60 and 70, but that's because I have a lot of surface area absorbing those chlorine destroying UV rays. As a result, I know I have to watch my FC like a hawk because I never want it to get close to the minimum, because I never want to SLAM the pool. In my case, I use the FAS-DPD test all the time; in fact, I've never used the simple chlorine test because I need the precision, and frankly, I want it. TC above 5 isn't good enough for me. If your minimum is 3, you could use the comparator test, and if it gets below 5, bump it up to 7. That would leave enough buffer. If you run the CYA any higher, you'd probably need the FAS-DPD test every time.