The first two seasons we had the pool up, the CYA level was at 40 both times. This time it's below 20 (not sure what it is exactly since the test only goes down to 20). The 2nd season we did very little backwashing at the beginning of the season because we used a cover. Unfortunately our cover got shredded and I slacked off and only used the solar cover last fall/winter, so we had a lot of vacuuming and backwashing to do. Is that the reason the CYA got so low? I know backwashing takes out a lot of water, but I didn't think it would be that low.
So at this point, what should I do? Start with 2 lbs and see what it is in a week? I don't want to be at such a low level that the chlorine doesn't work right but my kids are itching to get in the pool.