OLDER STYLE PUSH/PULL VALVE DIATOMACEOUS EARTH FILTERS HAVE THESE GENERAL COMPONENTS.

The older style DE filters had a PUSH/PULL Valve for activating backwash.
The Valve connects to the pump outlet & the water goes to the tank body & through the Valve, after being cleaned it then flows through the valve & back to the pool.
For BACKWASHING the valve is pulled open & the waste DE & dirt washed out...
To VACUUM TO WASTE, you have to disconnect at one of the two points shown & pump the water through another large hose to waste. or Take the lid off the filter & remove the internals & then replace the lid & lock in place. Now pull the valve to the backwash position & vacuum to waste.

Also see DE filter with MULTIPORT Valve