Sand is one of the best filter medias available for swimming pool filtration. During the course of its 3- to 4-year filter life, it loses the ability to trap particles. Starting out as a small square with jagged edges, each grain of sand is able to snag particles on these edges until through sheer wear and tear, the edges round off and the grains become like small pebbles. Your pool will begin to experience more episodes of cloudy or dirty water. When that happens, it's time to remove that sand.
Turn off the filter system. Screw appropriately-sized plastic, threaded plugs into the inside base of your skimmer and in the return inlet fitting. This will restrict all water flow while you remove the sand. You will have to remove the eyeball fitting that's in the return by holding the outer locking ring and gently turning the fitting.
Find a plastic threaded drain cap on the base of the canister. Remove the drain cap and allow the water inside of the canister to drain. Place the drain cap somewhere safe so it doesn't get lost in the grass.
Find the filter valve head, which sits on top of the filter canister. Unscrew all top screws around the perimeter of the valve head, making sure to mark the top and bottom sections with a piece of tape. You must replace it exactly as it came off or risk compartmental shifting within, which can lead to sand in the pool. Check to see if your system has one squared corner as opposed to all rounded ones. If it does have that corner, use it as a benchmark instead of marking it with tape.
Carefully lift and remove the entire valve head and allow the two sections of plastic pipe underneath it to separate. Using a scoop or your hands, remove the sand for disposal. Remember to use caution the lower you get in the canister, because the slotted fingers are at the base of the centered tube. They resemble the spokes of a wheel. Damage to any finger means replacement before moving on, or the sand will go through the hole in the finger and enter the pool.
Remove all of the sand from inside the canister. Each of the fingers on the center tube is on a pivot. Fold them up and remove the center tube. If they don't fold, unscrew each of them and remove the center tube.
Clean the inside of the canister with water and a scrub brush if necessary. Don't use soap. If storing it for the winter, clean the outside as well. Always allow plastic parts to dry well before winter storage. Any trapped water can freeze and crack the plastic part if stored in an unheated pool building.