You're not wasting the chlorine -- short of draining the water, there's no other way we know of to remove the ammonia or urea. This fall, though, you want to make a decision to EITHER maintain the water all winter (pretty easy once it cools -- you just can't forget!) OR to drain, store, and refill next year.

At this point, even though you aren't "wasting" chlorine, you are getting to the point where it would have been cheaper to drain and refill. On the other hand, if you were to buy the Intex salt system (Intex 54601EG Krystal Clear Saltwater System) @ Amazon. . . you probably are getting close to the point, where you wouldn't have to add salt, since all that used up chlorine, turns into salt.

Add some more borax, though. You don't want your pH that low, while you are cleaning up that mess.