Whats causes Chlorine to decay - Light, or Heat?

[Crimson]

Or Both?

Just curious. If Chlorine is kept away from sunlight, but in a hot environment (ie, a Shed @ 95-100 degrees) will it keep it from degrading? Or does both heat and sunlight cause Chlorine to breakdown?

 

[PaulR]

Chlorine in the pool will break down from UV light.

Bleach will also degrade from heat. According to information here, 10% bleach at 90F will degrade to 5% in about 4 months. You'd expect it to follow some sort of concentration-dependent decay curve, i.e. it would drop faster at first and slower later.

Other forms of chlorine (dichlor, trichlor, cal-hypo) have much longer shelf-lives, but of course they also contain other things you might not want to add to your pool.
--paulr