Vaccu flush system.
The marine vacuum flush system has 3 components. The head, the vacuum generator tank and the holding tank. Using about a pint per flush the system uses onboard fresh water. This feature eliminates raw water contamination and odors. The small amount of water per flush allows for a larger holding tank capacity than other systems, but may accumulate more sludge in the tank because there is less water used. Using a small vacuum generator tank to create suction, the head and the lines are evacuated into the small tank. When the vacuum tank is full it is automatically pumped into the larger holding tank. Typically they have a 3 to 7 amp draw on the power system.
While Vacuum is being maintained in the system the water level in the bowl can be raised by simply lifting the flush lever before use. Flushing is accomplished by pushing the lever down or pushing a button. The vacuum in the small tank is lost causing the head and line to be evacuated at a very rapid rate. The loss of pressure activates an internal switch in the tank to recreate the vacuum. Recharging the vacuum takes about one minute, depending on how long the run is between the head and the tank.
Forget About It For Boats is used slightly different with a vacuum system. The small generator tank always has sewage in it. To protect it and the mechanicals in it, ½ half cap of Forget About It For Boats should be added to the head when the head will not be in use between outings. That will help maintain the pump and keep that tank odor and sludge free. Because it uses less water there will logically be more solids to water ratio in the tank. Forget About It For Boats will be a great benefit in consuming the solids in the main tank keeping it clean and odor free. Extra care must be taken to insure nothing but waste and toilet paper is flushed in this system. The strong vacuum can suck materials into the lines that will get lodged in the line or generator tank.