Im building a new house and decided to try doing the plumbing myself. I found a lot of helpful books (including code books) and talked to a local plumber. He thinks I need a trap in the main drain before it leaves the house and goes into the septic tank. I dont see anything in the books on this. Im wondering if sludge will build up in there and also if the septic tank needs to vent.

Thanks, i really appreciate it.