macerator pump...only used to dump holding tank
, which--if you're in the US--is only legal
to do when in open sea at least 3 miles from the nearest point of land on the whole US coastline. If you're on inland waters, you won't need one.
At the risk of appearing to "sell" you something...if this is your first boat
with a toilet/sanitation system, I suggest you check out my book..see link in my signature below, just click on the title...which btw is a bit misleading 'cuz although it does deal with every source of odor
on a boat
and how to cure, or better yet PREVENT 'em, it's actually a comprehensive "marine toilets and sanitation systems 101" manual that explains the laws, describes all the types of systems and how they work
, and will help you learn how to operate and maintain your system to prevent 99% of problems instead of having to cure 'em. 'Cuz you get to do any preventive maintenance
on your terms when it's convenient...the need to cure a problem never happens when it is! Whether you buy it or not, I'm always glad to answer any questions.