The Formula dealer said everything checks out with the Vacuflush system but I haven't been able to empty the tank with the Macerator. I opened the seacock (discharge) and moved the "Y" valve to the Macerator. Do I need to flush the toilet while depressing the Macerator button?

My last boat had this set up...and yes in order for the macerator to work I had to power down the vacuflush and flush it to release all pressure before firing up the macerator.

If you have a Dometic "Vacuflush" you have to use a diaphram type discharge pump not a macerator. A macerator cannot pull against a vacuum. Also remember the discharge pump and the vacuum pump look almost alike but are not interchangeable. The inlet and outlet ports of the pump are threaded backwards of each other. One has left hand threads one has right hand.

That stinks. Hope you figure it out.

Here is the link for how the discharge is supposed to be set up for a Vacuflush unit. If this isn't the exact model poke around others are available. Download the PDF parts file. It will break everything down for you.

http://www.sealandtechnology.com/pro...ges.asp?pid=17