It does not deteriorate during the summer--if you lose any during summer, it's usually due to splashout, backwashes, leaks, etc. Draining and refilling water is the only REAL way to lower it.

It does occasionally deteriorate during the winter, in pools that are allowed to go swampy, but in those cases, the byproducts create huge chlorine demands on opening, so that's not a good option!!

Welcome to the forum!