Hello Peggie,there is an acumulation tank that the vacu flush is attached to and it
then goes to the bigger holding tank,which has the only vent on top.there are no
other switches and no tank gauge,I have installed a Gobios tank gauge and it shows empty?All of the threads I have seen talk about a vent loop of which there is none.
On the main breaker panel there is a switch marked maserator,when using the head
this has to be on for the vacu flush to operate,but this wont operate the maserator
unless the thruhull discharge valve is open and the switch marked empty by the discharge line is turned to the on position.