A pool closing service includes a deep clean, chemical treatments, and equipment winterization. The steps your pro will take look something like this:
Remove, clean, and store all removable components
Kill algae and bacteria with a chemical shock
Vacuum and deep clean the pool
Lower the water level
Drain and lubricate all equipment
Test and balance the water
Cover and secure the pool, including adding an air pillow if necessary
You should close your pool for the winter when you know no one will consistently use it and when the outdoor temperature regularly dips below 65°F. You must close your pool before a freeze. While it's true that if the filter is running, it won't freeze. But, if the power cuts out for any reason, the water will freeze inside the lines and likely wreck your equipment as it expands.
If you don't close your pool and you have plumbing lines with sitting water in them, the water will freeze and expand, where it can easily burst pipes and seals. Your pump, heater, and filter will take expensive and potentially irreparable damage, too. For example, repairing a pool heater costs $160 to $750, and installing a new pool heater costs $1,800 to $4,100. And winter conditions can damage your pool’s walls and structure, too, potentially even causing the walls to cave in.