closing after SLAM

[abfab]

I'm currently SLAMing the pool to treat algae. Once complete I plan to close the pool. In the past (new to TFP this year) I just took a water sample to the pool store and once they ok'd it I closed. For a couple of years I added algaecide but then someone told me its not necessary so I stopped. I didn't notice a difference when opening. I've never shocked before closing and would open with pretty nice looking water (green but no swamp or algae issue).

I'm not sure how to proceed this year. Do I have to let my fc settle back to normal (4-6), test chems (have k2006 kit) then bring up to shock level again, or can I close with my FC still high?
Why does pool school recommend bringing the chlorine back half way to normal? Wouldn't leaving it at a higher level be better to prevent algae?

 

[SunnyOptimism]

I don't close my pool (because of where I live), but one thing to remember is that you want to close your pool when the pool water is consistently 60 deg F or lower as that is the temperature at which algae really stops growing (it's still alive, just not willing to "party" when it gets cold out).

Also, since you're covering your pool, draining it partially and not circulating, it is best to keep a higher reserve level of FC in the pool that you normally would. Temperature-dependent degradation of chlorine slows below 60F and if the water is really clean, there shouldn't be much of anything that the FC needs to fight against. Since vinyl liners do get affected by higher chlorine levels, the half-way point between target FC and shock level FC is a good, happy-medium to leave the water out. The FC will definitely drop over the winter no matter where you start it at, but starting at that slightly elevated point gives you good assurance that you won't have a problem develop if you have a slightly warmer winter or some random day of freaky-high winter temperatures...

The use of algaecides (stick with Polyquat-60, not metal based ones) is more of an "insurance policy" against algae. If you're ok spending the money on it and using it, then it's not going to hurt anything.

 

[pwrstrk]

I would suggest raising your FC up to shock level. That's what I do and when I opened in the spring I still had 4ppm of FC. No polyquat was used.
I would wait as long as you can to totally close, by that I mean when the water temp is below 60. I waited till my water temp was 50. The water temp is key to closing and opening !
If you could add your location that will help us give you better advice as location can change advice you'll receive. ?