If you ask someone how to fix an air lock in your sewer line and they tell you, take their advice with a grain of salt. There's no such thing as an "air lock" in your plumbing lines, and anyone qualified to give you plumbing advice should know that. Although you'll never have an air lock in your plumbing, you can get a clogged vent. This can cause numerous problems and is likely what people actually mean when they say they have an air lock.
How Your Vent Works
A closed plumbing system simply wouldn't work. In a closed system, any water flowing through your drains or sewer line would create a vacuum and stop the drainage system from working properly. Your vent solves this problem.
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Located on your roof, your plumbing vent allows your plumbing to pull in fresh air. This air helps to apply downward pressure that aids in water drainage while preventing a vacuum from forming. It also gives sewer gasses a place to vent so you don't have to smell them. A blocked vent can't perform these jobs well.
Signs of a Clogged Vent
Slow drains are often a sign of a clogged vent, although the drain itself could also be clogged. If there is no clog in the drain or if all of your drains are running slowly, a blocked vent is typically to blame. A blocked vent can also make your drains stink. One stinky drain could be the result of a dry P-trap, but a whole-house smell is likely the vent.
Other signs of a blocked vent include gurgling in your pipes. You shouldn't hear gurgling in the sink when you flush the toilet. In fact, you shouldn't hear gurgling at all.
How to Clear a Vent Clog
It's not hard to clear a clog, but it does require you to get on your roof. This means you should always make sure someone else is present while you work and exercise extreme caution. Once you're in position on the roof, remove the vent cover if you have one and examine the vent.
If you see a bird's nest or other clogs that you can easily reach, remove them by hand. Then, shine a flashlight into the vent and look for clogs deeper in the system. If you see any, try getting to them and pulling them out with a plumbers' snake.
If snaking the vent fails, flush it with a garden hose. The vent may start to fill with water, but eventually, the weight of the water should dislodge the clog. You will probably hear a whooshing sound when it does.
When to Call for Backup
If you're uncomfortable walking around on your roof, don't force the issue. You can have a plumber do the job for you for around $100 to $200 on average. That's a small price to pay to remain safely planted on the ground. Of course, you should also call a plumber if for some reason you are unable to remove the clog or if you find other problems.
Preventing Future Clogs
Once you've got things working again, consider taking steps to prevent future vent clogging. One way is by installing a vent cover. Do so carefully, however, as the wrong vent cover can make things worse instead of better. Get some recommendations from your plumber before buying a vent cap.
For an even easier fix, place some screen over the top of your vent to keep out leaves, animals, and other potential sources of clogs without interfering with the airflow. If you live in an area with cold winters, it's wise to insulate your vent since ice can cause blockages as well.