Hi Oliver,
it is depending on the installation...but i'm sure yours is similar to mine. I had one and I was not lucky with it so I kicked it out again. I talked to a Jabsco guy and he said that this toilet is not so suitable for boats with a long pipe from toilet to tank. Like my bav 36 cruiser 11, which has a 2m long 38mm hose from the toilet up to the tank. Reason is that you cannot adjust the fill and the flush volumes and the sequence (it's 5 sec fill, then 5 seconds fill and flush together, you cannot flush without having filled before). The amount is just not big enough to get the waste over the highest point and in the tank. So it stays in the pipes... You would have to flush several times (which is not possible without filling before, the electronics only flushes after filling). So now you spend more water than you would need. I was told to use the quite flush model and I did and it's perfect.
Second thing is again the fixed fill and flush times ...in the night. You need to make a complete fill and flush action (5 seconds fill pump, 5 seconds flush and fill pumps together) - to get the bowl empty, even if it is only a small business - everyones awake for sure and the tank fills quickly. With the quite flush we only push the flush button for half a second only to get the toilet empty. In the morning we fill and flush some more water to get the pipe clean and everythings fine.
Oh and the quite flush has a 25mm wastepipe because of the better maccerator, so you need even less water to get the waste out of the pipes in the tank.
Hope this helps you
Jens