How do I back flush my pool?

Question:After a year, I am good at treating my in ground pool with chemicals to keep it crystal clear. I have the vacuum and skimmer working just fine. But, I've read a lot about back flushing the pump. What is this and how is it done? FYI - I have a 13,000 gallon in ground concrete pool with a DE filter (Diatomaceous Earth Filter).

Answers:
Turn off the pump. Turn the multiport valve to Backwash. Turn the pump back on for 3-5 minutes. Turn the pump off and turn the multiport to Rinse then turn the pump back on for a minute. Turn the pump back off and turn the multiport back to Filter. Turn the pump back on and add the required amount of DE medium to the skimmer on the pool to recharge the system.