Ok...the last 2-3 weeks, the pool's been going through 4-5 ppm of chlorine a day. Never less than 3.5 (on no bather days), around 5 on high load days.
Here's what i know and what I've done:
1) I test in the mornings as a general rule, usually between 6-7am. CC will be .5 3-4 days a week, 0 the other days. Never, not once, has it ever been more than .5
2) CYA is 50, has been the entire time, tested weekly at a minimum, double checked 2-3 other times. Wife has also performed the test, with the same assessment of the results...CYA of 50.
3) Pool is always crystal clear, even on mornings after storms have blown a few leaves in.
4) I've performed 3 OCLTs since I started noticing this high usage. FC losses of 0, .5, and 0
5) The pool gets direct, unimpeded sunlight from sunrise until 30-45 minutes before sunset. There are no trees or buildings nearby enough to cast any shadows or shade until very late in the afternoon, and the shade never completely covers the pool.
6) I've used 3 different brands of bleach during this time, each has been tested to confirm strength by testing FC 60-90 minutes after adding bleach, each time confirming FC was what would be expected for the given amount of bleach added, according to Pool Calculator.
7) My target each morning is 7-8 FC (lately 8, knowing I could expect to lose 4+)
I've got absolutely no indication that anything is using up chlorine...except for the fact chlorine is being used up. *heh* (Anyone remember A Few Good Men? Doctor, was there ANY sign of violence? You mean, aside from the dead body?)
Is it reasonable, given the long days of direct sunlight, that the pool is simply using that much chlorine daily? If so, would a slightly higher (60-70) CYA level be appropriate? Or am I overlooking something that suggests the pool should be shocked?
Thanks in advance for any assistance.