36F is not freezing. Even if the air temp hits 32F, it takes a lot of time for water in PVC pipes to freeze. How long will the temps remain low? If it's just a few hours overnight and then back above freezing by morning, then you hardly need any freeze protection at all.
I would check weather.com for your local conditions and then only set the pump to run when the predicted air temp hits it's low. For me, that's often 3 or 4am before the temps dip to freezing and then they're back up by 8am.
Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006