Originally Posted by Mr_Geenie
Toilet should be directly over the black tank.
RV toilets are pretty much a bowl with a pipe straight down to the black tank.
Otherwise you will need a macerator toilet with a pump to move the waste to the black tank. They are mainly used (in the US) if your bathroom is in a basement and your sewer connection is at ground level. Think of a toilet, blender, and water pump combined.
They are not inexpensive, and clog very easily.
Sanitary products and even toilet paper can clog it. There was one at a private marina I had a boat at. It was used part time by 15 boat owners, and it needed to be taken apart, cleaned out and reassembled about once a month. And there was a trash bag we were supposed to out our used toilet paper in that stunk to high heaven.
even boat toilets are a royal PITA.. a Homeless guy tries to catch a couple puffs of a cig in the bathroom and flushes a cigarette can mess up a boat toilet.. a candy wrapper even..
those macerator pumps often used in basement bathrooms of houses where the sewer line isnt deep enough are a PITA also.. they are very powerful motors and have a heck of a surge current on startup too.. they work best in a narrow deep pit as opposed to a shallow tank.. they also need LOTS of water to move the solids or they block up.. something not condusive to being on tank-water in a bus..