Remove the skimmer baskets and dump them out to prevent leaves and other large objects from going into your filter or back into your pool.
Turn the pump off if it is on and turn the lever on the pump so that it is in the "Backwash" position. Turn the pump back on and allow it to run until the water in the sight glass is clear. If you do not have a sight glass, check the water at the end of the backwash hose until it runs clear. Turn the pump off.
Set the pump to the "Filter" position for a minute then turn off the pump. Place the lever in the "Rinse" position and turn the pump on for two minutes. Turn the pump off and turn it back to "Filter."
Repeat the above steps to backwash and rinse out the DE until you are sure the system is completely clean and the backwash runs clear each time.
Set the pump to the "Filter" position and check the pressure gauge. The gauge should be around 10 PSI. If the PSI is high, add DE to your filter. Divide the filter's square footage by five. This will give you the number of pounds of DE to add to your filter.
Turn your filter on and allow it to run continuously until the water is clear. If you have performed all the maintenance on your filter and the PSI is 10, the problem is the pH of your water.