What Is the Gurgling Noise Coming From the Drain Pipe in the Attic?

Plumbing Vent Pipes

• The plumbing drainpipes you can see inside your house’s attic are vent pipes. While the vent pipes do connect to the drainpipes in your house’s plumbing, the vent pipes do not drain water out of any of the plumbing fixtures. Instead, the vent pipes allow sewer gases trapped inside the house’s drainpipes a way to flow out of the plumbing. Because the vent pipes’ openings sit above the roof, the vent pipes also allow fresh air to flow into your house’s plumbing, helping balance out any air that washes down the drainpipes along with waste water.

Venting Problems

• The plumbing vent pipes operate normally, without making any gurgling noises, unless an obstruction sits inside the pipes. Leaves or twigs that blow off nearby trees may fall down the vent pipes, over time forming a blockage. Animals may drop food or debris down the vent pipes. Installing a protective cap designed for vent pipes allows air to flow in and out of the pipes, but keeps debris from falling inside. In cold climates, during the winter, the hot and humid air that flows up the pipes may condense and then freeze, forming ice inside the vent pipes that blocks the air flow.

Health and Safety Risks

• Besides causing a gurgling noise in the vent pipes, as well as the plumbing fixtures’ drains, blocked vent pipes also pose a health and safety risk. Without a balance in air pressure in the house’s drainpipes, the water inside the traps or curving pieces of drainpipe may be pulled down the pipes. Without the water inside the traps, sewer gases inside the drainpipes can then flow out of the plumbing fixtures’ drains and into the house. Sewer gases can cause people to feel ill or in some cases asphyxiate. Explosive gases such as hydrogen sulfide and methane may be present in sewer gases, posing a safety risk.

Resolution

• You must climb onto your house’s roof to eliminate any obstructions in the vent pipes. During inclement weather, climbing on the roof involves increased risk, so be careful. Once you are on the roof, remove any obvious obstructions from the vent pipes’ openings. Look down the vent pipes using a flashlight. You may remove obstructions with a drain snake or by spraying water down the pipes, using a garden hose. If the vent pipes are clogged with ice, pour hot water down the pipes to break the ice up. Wrapping insulation around the vent pipes inside the attic also prevents the air from condensing inside the pipes.