How to drain your pool equipment in case of freezing temperatures:
The best thing for your pool is to keep the water flowing.
If the power goes out for more than 30 minutes to 1 hour then you will need to shut the breakers off and take out the drain plugs on your heater, pumps, and filter as well as open up the air relief on the top of the filter.
After you've done that, put as many blankets as you can over the top of the equipment to form an insolated dome over the top.
Here are pictures of where the drain plugs are located:
Heater and Pump Drain Plugs
Pump drain plug
Wide shot of heater drain plug location
Heater drain plug. Maybe facing down on some heaters.
Filter drain plug
* There are many types of air reliefs. They have a screw or lever or twist fitting. All are on top of the filter.
Be aware air reliefs and plugs may be frozen. Pouring hot water on drain plugs may assist this process. If you can't unscrew them the best you can do is try to remove most and cover all the equipment with blankets.