[Salt shaker]

hi all, new here with a new to me 3100 '94. boat has a vacuflush and macerator and im just wondering the best way to use and maintain it. the first time i tried to pump out, nothing sucked, and putting water in the waste hole, it just backed up over the gunnel. a freind with a a '96 helped me but was confused also, so i figured id ask. i think i have that valve flipped correctly now. also, what do you put in the tank and how often. a freind recommended the west marine treatment stuff.

any help / advice would be great! thanks