My breaker box has a 2nd timer I can use. Hoping I don't have to run my pump 24x7 like I did last year..If I cut it back in a week it would start turning dark and chlorine would be nothing..
Also I have a heater that also does the hot tub, any concerns with 100 degree water going through it?
I don't have a heater so I can't say with 100% certainty, but I can't imagine any issue 100 degree water would cause. The owners manual even specifically mentions that you have to install the SWG cell
after a heater to prevent the freshly chlorinated water from damaging your heater. Not sure if that's from a higher amount of chlorine or a higher pH or what, but the manual does mention installation with a heater.
About the water turning "dark", how much chlorine were you adding, what was your CYA at at the time, and did you preform a SLAM to completion? You really shouldn't need to run your pump 24/7 except to mix up some chemicals like freshly added salt or CYA.
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Also, when you pick out your SWG, make sure its rated for at least twice the volume of your pool. Yours is an 18k pool, so while you could get away with the RJ-30, the RJ-45 would be better. The more powerful the SWG, the lower % you'll need to run it at (longer cell life), and the less time you'll need to run your pump for chlorination.
You can get a Circupool RJ-45 here
CircuPool RJ-30 Saltwater Chlorinator for up to 30000 gallon salt water pools for $800 through a sale that ends 3/19/18. Just select the upgrade option to upgrade from a RJ-30 to RJ-45 for $1 more.