How to Unclog a Vent Pipe

When your drain vent is clogged, you’ll definitely have problems in your plumbing fixtures. How to Unclog a Vent PipeA clogged drain vent is characterized by gurgling sounds and sewer smells from the plumbing fixtures. Plus the fixtures might start draining slowly.

If you have plumbing stack vent problems then you can try fixing it by yourself before seeking the services of a professional plumber.

Related: How to Get Rid Of Sewer Smell in Bathroom Sink

How Does a Drain Vent Work?

A drain vent is very important component of a drainage system. It’s also known by the term ‘plumbing vent’. I guess that you can easily locate the drain vent extending about six inches above the roof.

The drain vent and drain pipes work together to remove waste, water and gases from the toilet, sink, bathtub and floor drains. While the drain pipes channel used water and debris from the plumbing fixtures, the drain vent provide an escape route for sewer gases.

Connecting the roof vent to the drain line is the plumbing stack or vent stack. Whenever you flush a plumbing feature, air is sucked behind where it aids in pushing waste down the drain line. Sewer gases and odor escape through the plumbing stuck as the waste water runs through the drain line.

Drain vents also work with drain traps to keep your house free from sewer odor. Whenever you drain a plumbing fixture, water is retained in the drain trap. As long as the drain trap is filled with water, sewer gases won’t escape into your kitchen, toilet or bathroom. So, when the drain line is dry, the only escape route will be through the drain vent.

How to Know That Your Drain Vent is Clogged

The drain line and drain vent are designed to function together to get rid of waste and smells from the plumbing features. So, whenever there’s partial or complete blockage in the drain vent, the drainage system will start behaving abnormally.

Though you may not be a plumber, it is very easy to know when there’s a problem with your drainage system.

Below are 3 telltales that the drain vent is blocked.

1. Sewer-Like Odor

Sewer-like odor which intensifies in the toilet, bathroom and kitchen is a good telltale that the drainage system has a problem.

The most likely explanation for sewer gases in your house is pressure buildup in the drain line. This can be due to a blockage in the drain vent. When the drain vent is blocked, sewer gases will raise up through the sink, toilet and bathroom.

2. Gurgling Sound

One drain vent can serve several plumbing fixtures. If you drain your toilet and hear a gurgling sound in the nearby sink or bathtub, that’s a sign of a clogged vent. If the drain vent partially or completely blocked, sewer gases escape through alternative openings. This could be either the toilet, sink, bathtubs or floor drains.

3. Slow Drain

When you drain a plumbing feature and the water trickles down sluggishly, then there could be a blockage in the drain pipe. If the drain pipe is not blocked, the problem could be a blocked drain vent.

A blocked vent results in pressure build-up inside the drain pipes thus hindering efficient draining.

How to Unclog a Vent Pipe

Whether your rooftop drain vent has cap or not, it is exposed outdoor substances and small animals. Over time, the rooftop vent collects leaves and flowers from the surrounding trees or nesting birds. Most often, these substances find their way into the drain pipe where they’re flushed away.

If the substances pile up and are not flushed out into the drain pipe, then the drain vent could end up being clogged.

There’s also a possibility of a tennis ball, bird or rodent carcass getting trapped inside the drain vent. While carcasses may decompose and get drained, a tennis ball won’t come out until you remove it from the rooftop.

If you’ve a height phobia, then you can call a professional plumber to unclog the vent. If you can do it yourself, then here are the steps to follow.


  • A ladder
  • Garden hose
  • Plumber’s drain snake
  • Flashlight
  • Screwdriver
  • Gloves and helmet

Step #1

Position the ladder on a firm base and about 75 degrees incline with the ground. Secure the bottom of the ladder with rope that is tied to fixed wooden or metal posts. The top of the ladder should extend with at least three steps above the contact point with the roof.

Step #2

Carefully go up the ladder while carrying the screwdriver and garden hose. The nozzle of the garden hose should be closed and the tap turned on. Open the vent cap and place it on the roof so that it won’t slide down.

Step #3

Using the flashlight, check what inside the vent and reach out with your hands to remove whatever you can.

Step #4

Insert the garden hose nozzle in the vent opening and turn it on to a high pressure jet. Most likely the pressure from the jet will push the clog down the drain vent and then into the drain pipe.

Step #5

If water fills up the drain vent, that’s an indication of a more compacted clog. Clearing a compacted clog will require greater force. That’s where a drain snake comes in (you’ll have to go down the ladder to get the drain snake). Now, insert the auger into the drain vent and rotate the crank until it reaches the clog.

You know that the auger has reached the clog when you experience some resistance. Rotate the crank in the opposite direction to retract the drain snake. Remove substances that have been grasped by the auger and repeat the process until you don’t feel resistance.

As you remove the clog, you’ll notice that the water that had filled up the vent will start trickling down. That’s an indication that the clog has been cleared.

Step #6

Finally, flush the drain vent with a pressurized water jet to drain down the already dislodged clog. If water does not back up, then you have successfully unclogged drain vent. Now you can descend down carefully while carrying your equipment.


If you experience sewer smell, gurgling and slow drain from your plumbing fixtures, then your roof vent must be blocked. Efforts to resolve these problems from the inside will prove futile.

To unblock the roof vent you’ll have to go up the roof and remove the clog using a garden hose and plumbing snake. If you have a height phobia, then you can contact a professional plumber.

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