Chlorine eats away at seals and gaskets. The hot tub’s pumps, jets, heaters, and plumbing need those rubber and plastic components to stay snug and leak-free. When you drown them in extra chemicals, they start to break down, which can eventually lead to leaks.
It ages your cover faster than you can say “spa day.” Chlorine vapor doesn’t just vanish; it lingers under the cover and slowly deteriorates the material and hardware that keeps everything together.
Chlorine corrodes metal parts. Heaters, fittings, and hardware are especially susceptible when sanitizer levels are too high, especially if other water chemistry elements are out of whack. Rust and corrosion follow.