All modern plumbing systems in residential construction have a plumbing vent. It doesn’t just vent unwanted odors from the drainage system to the outside; it actually serves an important purpose by supplying air to the system.
The plumbing drainage system in your home is actually called a drainage, waste and vent (DWV) system. When water flows down the piping, an air supply (vent) is needed to allow the water to flow. Think of the vertical pipe as a drinking straw. If you plug the top end of a straw, liquid won’t drain from it.
The DWV system in your home consists of a series of pipes connected to each fixture; they extend above each fixture, and the system terminates at an open pipe that extends through the roof. This piping allows air into the system and prevents unbalanced pressures in the piping.
The vent also prevents the system from drawing water out of a trap at the fixture with the characteristic “glug-glug-glug” as the drain gasps for air. Plumbing traps should drain smoothly and never “glug” or gasp for air.
If your home has a drain that empties slowly or gurgles as it drains, this may indicate a venting problem. If you flush a toilet and the sink gurgles, there’s definitely a vent problem. Have a plumber check this.