Chemicals for Winter

[perryy]

I leave my pool open for the winter, just for the appearance. We won't swim again until probalby May here in central NC. I've not added any chems since the fall. When the water temp was in the 50's or 60's I got some green algae that is still there. It comes off the liner easily (where the Polaris works the most, it's clean), but it's more stubborn on the plastic steps and the Polaris exterior. Water temp is now at 39. To get rid of the green, should I add bleach or an algaecide? pH is 7.8, TA is 70. If bleach, what chlorine level is needed? CYA is probably about 80.
Thanks,
Perry

 

[JasonLion]

I would start off by lowering the PH a bit, say into the 7.4-7.5 range. Lowering the PH will help the chlorine be more effective.

The regular shock level for a CYA of 80 is FC of between 15 and 20. With the water that cold the algae will be growing very slowly and it should be fairly easy to get rid of. You will also need to brush everywhere while the chlorine level is high to make sure none of the algae in the biofilm on surfaces survives the chlorine.