If you can easily drain, that might be the best thing to do.
Keep in mind that if your CYA was REALLY high (>150ppm) you may have a lot of ammonia in the pool. There's no easy way to tell, at present, but if you do it will *still* take enormous amounts of chlorine to clean up.
Also, if you drain 1/3, your CYA will only go from 90 to 60 -- still quite high if you plan to use stabilized chlorine.
Under the circumstances, you might want to add a 10 gallon dose of bleach in the late evening, and then test an hour later for both FC and TC. Test again the following AM within 2 hours of sunrise. Then post the results. Those results will give us a much better idea of what your situation is.
Ben
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