Basic plumbing on trawler

Hi there, greetings from Buenos Aires! I would like to redo the plumbing of my boat: there are two heads and one galley in my 50 ft steel trawler. Toilets have electric macerator pumps which take water from the river and discharge to the same. Grey waters are also discharged overboard. I would like to install a holding tank and have some questions I request you to help me with: will the macerator pump be capable of evacuating the bowl and moving the water into the tank about 12 feet away? ... or should I install a relay pump amid-ship? Given the distance from the toilet to the tank: If I cannot drain the pipe (or hose) from the toilet to the tank by gravity (slope) will the toilet need to be flushed with a lot of water to prevent nasty smell from water standing in piping? I know there are airplane like (vacuum driven toilets)... but they are far out of my reach, and I honestly would like to keep the system as simple, as possible.
All input will be appreciated!

Kind regards

I don’t know about toilets but the Raritan Marine Elegance will pump that far easily. I have installed them in previous boats and have one in my boat waiting to haul my boat for winter and I will install it then. You really want the discharge hose to slope down to the holding tank so the sewage will gravity drain and not sit in the hose. Otherwise you will have to do extra flushing to pump the sewage into the tank and have clean water sitting in the hose. When you put the new holding tank in it is best to put a vent to each side of the boat and make them at least 1” diameter, that will promote air getting into the tank and will help aerobic bacteria growing. It is the anaerobic bacteria that causes smells.

Length of pipe will be less a problem than slope. If you can keep a steady downward slope from the toilet to the tank it will naturally drain down.
For smell there is no reason to have any issue if you use good quality sanitary hose.

L