We were having problems with our macerator and purchased a new one exactly the same. This time we put it as close to the tank as possible with the intake at the height of a full tank. I also put in an additional valve to shut off any possible air coming in from the deck fill and slowing the siphon action down. It catches the waste quickly and when I hear it start to whine from an empty tank I shut it off. It's much better than the way it was.

I also changed the switch to a push button closer to the pump so I could hear it better. Now I have to keep my finger on the button until it's empty. This way there's no chance of running the pump dry.

Works great with the changes.