The only practical way to lower it is to drain and replace water . . . which is pretty wasteful and expensive, and which can destroy vinyl pools if not done professionally.

There is a way to drain in place, using a tarp larger than your pool, if it comes to that.

BUT . . . there is another alternative:

1. Buy a K2006 and find out what your CYA level really is -- you'll have to do a 1:1 dilution with tap water, test, and then double the reading. (Test kit info page, here. You'll also need the K2006 and CYA test in order to know how much to drain.)
2. Adjust your 'ideal' chlorine level according to the "Best Guess Chart" in my signature.
3. Chlorinate just one time per week with bleach or cal hypo (or get an SWCG)

Doing so is a lot less expensive than draining and refilling, and won't waste water. Your CYA will gradually go down over time, especially if you are backwashing a sand filter.