Your sand filter dial head has the following positions:
Filter position: Used when you are running your pool, and need the pool water to be filtered. This is the most commonly used position.
Backwash position: This position is only used when your filter is dirty and you want to clean the sand in the filter. Water is reversed through the sand, and lifts out any dirt. It is then discharged out of the waste pipe.
Rinse Position: Used only after backwashing. Does same thing as the “filter” position, only water goes out of the waste pipe instead of back into pool.
Winterize position: Used in winter to relieve pressure off the seals, so they don’t flatten and leak over time. This position also lets air into the filter, to help drain the water out of your filter during winterizing.
Whirlpool position: Used when you want the water to bypass your filter. It is most handy when you’re diagnosing pressure problems, or checking how dirty your sand is.
Drain position: Use this position when you want the water from your pool to not get filtered, but go directly out your backwash waste hose. This position is also handy if you are vacuuming up debris that you don’t want in your pool or filter.