Plumbing roof vents allow sewer gases to escape the plumbing system and allow air into the drainpipes to prevent the formation of a vacuum that causes slow draining. If a vacuum forms because of a blockage, it has the potential to open traps and allow sewer gas inside the house.
Because roof vents are open to the outside of the home, they sometimes plug. Leaves, pinecones and other natural debris sometimes fall into the vent to cause the problem. Birds and rodents sometimes choose to build a nest in the warm pipe. Sometimes, a small animal falls into the opening and plugs the vent. Inside the home, the resident sometimes hears gurgling sounds, observes changes in water level in the toilet, smells a rotten egg scent or finds fixtures that are not draining.
To restore proper operation to the drain system, it is necessary to open the vents. If the homeowner chooses to do this job for himself, he accesses the vents from the roof. Sometimes, a garden hose with a sprayer attachment is sufficient to wash the blockage away. At other times, cleaning the vent requires using a plumbing snake. Since the lines get larger as they move away from the vent, pushing the plug through to free it does not cause it to lodge further down the drain.