Balance Your Pool's Chemistry
Adjust the pH to a level between 7.4-7.6 (7.5 optimal)
Adjust Free Chlorine to a level between: 1-3 ppm
Adjust the alkalinity to 80 to 140 ppm Free Chlorine: 1-3 ppm
Adjust the Calcium Hardness to 220 to 350 ppm.
In order to kill bacteria and algae shock your pool with extra strong chlorine.
After few days add a winterizing algaecide but first confirm that the chlorine level is between 1 and 3 parts per million. Presence of algae will affect your pool negatively by discolouring pool water, bad smell and clogging the filter. Use extra strength algaecide for this purpose.
Clean & Backwash Your Pool Filter
After backwash and rinse, place the valve to the "winterize" setting on the top mount valve. This will drain water from the valve.
Now completely drain the water from the filter tank. To do this you need to remove the drain cap on filter barrel bottom. Lastly disconnect all of the hoses from the filter. Place sand filter, pump, hoses, and the drain cap in a dry, safe place.
Lower The Water Level
Drain Your Pump, Filters, Heaters, and Chlorinating Equipment
For a DE pool filter or a cartridge filter, take the grids or cartridge out, clean them, and store them away for the winter.
Take these plugs out of these units because If you plug them back up and water get into them, they might freeze over and crack your equipment.
Put the plugs in the pump basket so you know where they are next spring.
For sand filter, put the Multi-Port valve in the "winterize" position and remove pressure gauges if any.
After draining the pump, turn it on for a second or two to get the water out of the impeller.
Check your heater instructions to see whether the manufacturer recommends removing the heater tray.
Blow Out The Water Lines
You can blow out the plumbing lines for pool winterize using, again, your Shop-Vac. Use the discharge of the Shop-Vac to blow water from each plumbing line of the filtration system. You'll see bubbles as the water is purged from the lines. Ensure each plug has "O" ring or gasket for a tight fit. It is important otherwise water can go back into the line creating issues in future.