Turn off the pool pump. Pull on the ring of the pressure release valve to release the pressure inside the pump. When the gauge reads "0," the pump is ready. Remove the cap on the drain spigot on the bottom of the pump.
Remove the multiport valve from the top of the pump tank. Use a plastic scoop or a plastic cup to scoop out the old sand. Stay away from the sand pipe laterals in the center of the pump. Work from the outer sides of the pump.
Remove the remaining sand on the bottom of the pump, using the shop vacuum, and gently vacuum the laterals to remove any sand wedged in between the fins. Do not bend or break any of the fins or you'll have to replace the lateral pipe.
Replace the cap on the drain spigot. Cover the top of the lateral pipe with a rag or a plastic cup so that the new sand will not get inside the pipe. Fill the pump up halfway with water.
Slowly add the No. 20 silica coarse sand to the pump. Add all the recommended sand.
Remove the cup or plastic cup from the top of the lateral pipe. Replace the multiport valve. Move the handle of the multiport valve to "filter." Turn on the pump.