This is not Minnesota. Most San Gabriel Valley pools stay full. Winterizing here means chemistry, freeze nights, and equipment that is not left wet in a cold snap.
What we actually do here
Drain-and-antifreeze winterizing is for climates that stay below freezing. In San Gabriel, Alhambra, and Pasadena, a hard freeze is rare and short. We keep water in the vessel so the shell does not take ground pressure. We raise sanitizer slightly, balance pH, lower the pump run time, and watch the weather. If a freeze warning is posted, we circulate overnight and open equipment drains.
If a freeze night is coming
Run the pump. Moving water is slower to freeze than still water in a pipe. Drain the filter tank and heater heat exchanger if the unit will sit. Never use automotive antifreeze in pool lines. If you blow lines with a compressor, that is a job for a technician — over-pressure cracks fittings.
Covers and leaves
A winter cover is optional in this climate and useful if trees hang over the pool. A cover that sags into the water becomes a debris net. Pull it taut, keep the water at the skimmer, and do not let the pump starve. Our bi-weekly winter route still brushes the tile line — that is where calcium and algae start when the sun is low.