i'm not sure that blowing it would go down to the overflow, at least not all and not immediatly. most of it will go back to the BottomI did not siphon the sand. I blew it off and let the mess go down the overflow to the first chamber when the 5 micron socks are.
This is what I used:
Honritone 4 Inch Ring by 15 Inch...
or with the same system even the sand Will go down to the sump