This sewer line cleanout guide should help ... as well as traps that fill with water to prevent sewer gasses from backing into the home. These fittings and fixtures are all pitched toward the ...

Next, grab the necessary PVC fittings for the cleanout as well as a fitting to connect to the existing sewer line. Assemble all of the fittings and make the connection to the existing line.

Fittings for water lines are different than those for drain ... but the ones you might need to remove temporarily, like cleanout plugs, are threaded. Here are the most common drain fittings.