I don't know how I missed this post-- I'm sorry!! This should bump it to the top, though. If your CYA is really 150, the only way your pool is going to be manageable is to drain/refill water. I definitely would not drain it att at one time because if your water table is high, it can "float" the pool. Rather, if possible, I would do two 50% drains, which should drop it down to a much more manageable level.

Janet