That's fairly low, but does indicate that you probably had a higher amount earlier. It will take around 2-3 ppm FC to get rid of that relatively small amount (0.25 ppm) of ammonia, so you're almost there! If you've also got measurable CC, then it will take a little more than half that amount to get rid of it as well.
I find it surprising that even 15 kids could urinate enough in a 22,000 gallon pool to have it consume this much chlorine (one quart of urine would take around 2 ppm FC in your pool volume). I think that when you initially opened the pool you had ammonia (from degradation of CYA over the winter) which you then mostly took care of (with lots of chlorine) and then the kids came and added more (mostly urea) into the pool and you are now taking care of that. Urea can take longer to get rid of than ammonia, perhaps taking 1-2 days at shock level compared to just hours for ammonia.
As Jason said, keep your chlorine level up at shock level until three things occur: 1) the pool becomes crystal clear, 2) you measure minimal (<= 1 ppm) drop in FC overnight and 3) you measure minimal (<= 0.5 ppm) CC.
Richard
I find it surprising that even 15 kids could urinate enough in a 22,000 gallon pool to have it consume this much chlorine (one quart of urine would take around 2 ppm FC in your pool volume). I think that when you initially opened the pool you had ammonia (from degradation of CYA over the winter) which you then mostly took care of (with lots of chlorine) and then the kids came and added more (mostly urea) into the pool and you are now taking care of that. Urea can take longer to get rid of than ammonia, perhaps taking 1-2 days at shock level compared to just hours for ammonia.
As Jason said, keep your chlorine level up at shock level until three things occur: 1) the pool becomes crystal clear, 2) you measure minimal (<= 1 ppm) drop in FC overnight and 3) you measure minimal (<= 0.5 ppm) CC.
Richard