When you flush a toilet and the shower drain burps air at you, that is air being sucked through the shower’s P-trap. The vent is supposed to supply that air, but it can't. So the system cannibalizes air from the nearest sink or tub, sucking the water seal dry. That seal is the only thing stopping sewer gas from entering your lungs. Lose the seal, lose the war.
When the vent is clogged, water flows like a straw with your finger on the top. It glugs. It hesitates. It stops. So, what clogs a pipe that never actually touches water? A surprising amount of organic warfare. drain vent clogged
Respect the vent. It is the only thing standing between you and a house that smells like a petting zoo. The cheapest insurance policy you will ever buy is a vent cap . It is a simple cast-iron mushroom or a stainless steel screen that screws over the top of your roof vent. It costs less than a pizza. When you flush a toilet and the shower