Here are my numbers first:
FC 4.5 (added 3L two days ago because we have had allot of rain and the pool was only at 2ppm (and I wanted to fill my jugs before the weekend rush)
CYA <5 (but something there because it is just barely cloudy on the test)
Water Temp 24C
Well I did pickup some CA to add to my pool because I know I am below 10ppm. I have not added any though because I have just a few more questions about it. My pool is 79300L and with a level of CYA 0-10ppm the pool calculator tells me I should be at 1-3ppm FC and shocking to 10ppm.
When I opened the pool on May 12, 2012 the water was clear so I filled the pool and added 10L of 12% Bleach. This was the only time that I shocked the pool because since then I have been able to maintain a FC level between 2-3ppm with minimal effort and have crystal clear water. I have been adding 1.5L (often less ) of bleach every other day when the pool is in use and the cover was off for 8hrs or more. The pool gets 8hrs of direct sun a day with a solar cover on so I thought 1.5 liters of bleach every other day when in use (2 adults and 2 children) was reasonable. I manually vacuum every other day and brush the sides at least once a week. When I use the solar cover I can go 2 or 3 days without the need for adding bleach.
I run the filter at 1500 and shut it off at 2300 every day. The solar cover keeps the water at about 25C while the average outside temperature has been around 22C. I think turning the filter on at 1500 helps mix all that warm surface water from the solar cover into the pool which has help allot with the temperature.
So I guess my question is this. Do I even need to add CYA if my chlorine use is fairly low? I have seen the FC/CYA chart and by adding CYA I am stabilizing my chlorine. But by doing so that stabilized FC is tied up by the CYA and can't oxidize during this period hence why you need to maintain a higher FC level. So this is where I am confused as to the purpose of the CYA. Yeah it stabilizes the FC but I need to have more FC in the water while the stabilized FC is tied up by the CYA? Am I missing something here?
Or is my FC use actually considered high and I just don't know it because I am a total NooB!