chem geek said:Any idea what the water temperature is? Also, any idea of the typical FC level in the pool and the pH? Do you know the size of the pool in gallons? Does the pool have a sand filter backwashed weekly or a DE filter cleaned regularly (both of which would dilute the pool water)? Maybe the slow oxidation of CYA by chlorine becomes more noticeable at higher temperatures, but something still seems different here. Perhaps really strong sunlight also leads to some breakdown over time. We'll have to keep track of more pools to see if we can figure this one out!
My parent's pool? Here's my best estimate:
Temperature - Around 88-92F in the summer months, 60's 70's in the winter months.
Size - About 20,000 gal
They have a DE filter.
I wish I would have been testing my CYA more regularly so I could have tracked it as a function of Chlorine level and temperature. I tested it every week for the first couple months, but when it didn't seem to change (and I read that it shouldn't change) I stopped testing.
However, I do love a good mystery.