Do you know where your main plumbing vent is? Many people don’t, as is evident by the picture below, many times I see the main plumbing vent covered by stairs, paint, bushes and vines, trim, and almost anything else. Why is this an issue? Your main drain vent allows your plumbing drain system to work properly. As you flush a toilet or run a sink, the water going down the drain creates suction. The main vent helps the entire system drain properly right where it leaves the home.