FC level of 31 is still way too high for CYA level of 80. Also, fifteen minutes isn't enough time to mix your water and chemicals. Starting and stopping every hour is going to burn out your pump motor prematurely. Most people run the pump just once per day. Do a search for pump run times.
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FC 31 is the recommended level for a SLAM according to poolmath and Pool School - Chlorine / CYA Chart
As regards to the spa - I want to SLAM the spa and the pool simultaneously since I don't want any algae contamination from the spa to the pool. Maintaining both spa and pool water at the same concentration of FC is my aim...