Bottom line: No air, no drain. Check the vent before you dig into the pipes.
: Severe winter weather can cause frost or snow to block the vent opening on the roof. clogged drain vent
Your plumbing works the same way. The (or DWV) is a network of pipes that lead from your sinks and toilets, through the house, and up through the roof. These pipes allow sewer gases to escape safely into the atmosphere while letting fresh air enter the system. Bottom line: No air, no drain
Birds, squirrels, or rodents may use the vent for shelter and become stuck or build nests inside. Bottom line: No air