Getting ready to close soon. Water is in low 50's so I'm turning off the swg and will use liquid shock for Cl until close. Can I use older gallons of shock purchased in August or should I get new? I read in pool school that older bottles of Cl may be lower in concentration, but is there any other problem with using it up? Also, if I do need to get new Cl how should I dispose safely of the old bottles?
Thank you

As long as the liquid chlorine has not gotten excessively hot, or very warm for many days, it should be fine to use. The Sodium hypochlorite disproportionates into chloride and chlorate.

Nothing wrong with using it. To play it safe, simply test the FC level a half hour or so after dosing just to make sure you're getting what you think you're getting.

Nothing wrong at all with using it i never throw it away what i have left from this year will get used next year.

Use it up. How else will you get rid of the stuff besides pouring it in the pool? If you save it until spring it will probably just be salt water by then.

The only thing to worry about is that it will have lost some of it's original strength, so you may need to use a little more than you would otherwise have needed. The loss in strength shouldn't be dramatic over six to eight weeks, enough to be able to notice a difference, but still reasonably strong.