If the alkalinity of your fill water is 220, then you're going to find yourself constantly fighting high alk...so if it's not causing any problem for you right now, I would leave it alone.
As for your CYA level, I'm not sure how you're getting a 10-15 reading, since most testers can't distinguish levels less than 30 ppm, but you can either let it continue to rise by using trichlor, or you can just add CYA alone--it's often labeled as conditioner, stabilizer, or balancer, but if the active ingredient is cyanuric or isocyanuric acid, that's what you're looking for. You can either add it through the skimmer and then not backwash/clean your filter for a week or so to give it time to dissolve, or you can put it in an old sock and tie it in front of a return. Either way, don't go too high--as your CYA level rises, so must your chlorine levels, so I wouldn't go over 40 ppm or so unless you have a good reason.
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