If you're hearing gurgling sounds after using your sink, shower or toilet, there are several possible causes. The most common cause of slow-clearing drains is an obstruction caused by a build-up of grease or waste on the inside of the pipe. A thorough drain cleaning using a drain snake or water jetting can clear the residue from inside the pipe and get the water flowing again.
Vent Stack Obstructions
In order for wastewater to flow out of the home, air must be able to fill the vacuum left behind by the escaping water. A vent pipe serves this purpose by extending from drainpipes out through the roof of the house. All plumbing fixtures must be connected to the main vent pipe through a re-vent pipe which that spans across to the main vent stack that exits through the roof. In some cases, usually with basement plumbing, the vent may exit out of a side wall if allowed by local building codes.
If you hear gurgling sounds when you flush a toilet or turn on a faucet the vent pipe may be obstructed and in need of clearing. For example, there could be a birds nest obstructing the pipe, or it may have been damaged by a storm. It could also be a sign that the plumbing system is faulty needs a new vent line. Another symptom of an obstructed or insufficient venting is plumbing odors, as vent pipes also allow fumes to exit through the airway behind the draining water. In either case, a plumber should inspect the vent pipes to ensure they are working properly.