Jao,
https://www.westmarine.com/west-advisor/Selecting-a-Sanitation-System.html might be a good start.
Raritan is a well known manifacturer of many marine toilet components with some technical article
https://www.raritaneng.com/blog/But mere google search (
https://www.google.com/search?client=firefox-b-d&q=how+to+plumb+a+marine+holding+tank) will give you plenty of hints.
In the US, you need a holding tank (you can not discharge in the 3 miles coastal zone, and there is many additional limitations), but most boats (including mine) usually have a dual discharge - since it is common to sail much beyond this limit - especially with a nice cruising boat like the J/30.
The vented siphoned loop is likely the most single important aspect of the setup... no one want to sink through their heads ... .
cheers,
-- Georges
