Vent pipes -- a small pipe sticking out of the roof of a home -- is crucial for the proper function of the home's plumbing. Credit: John Holyoke / BDN

Many things can cause plumbing problems in your home but one you may not have considered is a lack of air. That’s because it takes a constant flow of air to maintain the pressure through your entire plumbing system needed to keep water and sewage flowing in the proper directions.

So, how do you make sure everything is running correctly? It all comes down to the plumbing vent pipe.

What is a plumbing vent pipe?

Where can you find your plumbing vent? It’s simple: Look up at your roof. The small pipe sticking straight up is a plumbing vent pipe. Every home should have one in proper working order.

The plumbing vent pipe is a simple section of pipe that comes out of the roof of your house and extends a foot or so above the roofline. That pipe is connected to the drains on your sinks, toilets, showers, bathtubs and washing machines by a series of smaller pipes at a point above the drain traps on each fixture. Drain traps are those curved sections of pipes below plumbing fixtures. They are designed to hold a small amount of water each time water drains through them. That retained water acts like a seal to keep sewage gasses from backing up into your home.

What does a plumbing vent do?

A plumbing vent protects the drain traps. The vent allows air to escape to the outside as water pushes through the trap. If that air had no place to go, it would create a suction effect and pull too much water out of the trap. Without the proper amount of water in that trap, those sewage gasses are going to drift right up the drain and into your home.

“A plumbing vent is necessary for your sewage system to function as designed,” according to Dave Boucahrd, a home repair clerk at S.W. Collins Co. in Fort Kent. “If it’s not working you are going to have trouble.”

A build-up of sewar gasses will also make it difficult for water to drain at all because those gasses can create enough air pressure to force liquid back toward a plumbing fixture.

What happens with a clogged vent?

Because the outlet for your plumbing vent pipe is exposed to the elements, it can get clogged. Any number of things can clog your vent pipe — birds or rodents building a nest on top of it, leaves or other debris falling into it or a build up of ice or snow in the winter months.

Regardless of what causes the clog, it’s a problem because now the air building up in your drains has nowhere to go. Signs your vent is clogged include gurgling sounds coming from the drains, standing water in sinks and bathtubs, slow drains and sewage odors from the drains.

The surest sign of a blocked vent pipe is that none of these issues can be resolved by cleaning or plungering your drains. In fact, you can do far more harm than good to your pipes by trying to remove a drain clog that does not even exist with repetitive treatments with chemical drain cleaners.

So if your plumbing fixtures exhibit symptoms of a clogged drain that are not resolved with a single drain cleaning treatment, you likely have a clogged vent pipe.

Clearing a clogged vent pipe

Because accessing your vent pipe means climbing up on your roof, you should take great care if you plan to do it yourself so you don’t fall. There is also the possibility of being exposed to a rush of harmful sewage gasses when the obstruction is removed.

This time of year in Maine it is not uncommon for enough frozen water or snow to accumulate in the pipes to clog them. But luckily there is a simple solution for that — pour hot water down the pipe until the ice or snow is cleared. Frozen vent pipes can also be cleared using a heat gun or blow dryer.

If the clog is caused by some sort of detritus that has gotten in there and you can reach it, simply pull it out. But always remember to never stand directly over the pipe to avoid any unease sewage gas.

When in doubt of your roof climbing abilities or how to remove the clog, the best plan is to call in a professional plumber.

Vent pipe maintenance

The good news is that unless there is a problem, vent pipes really don’t need any maintenance.

“If your pipe is visible from the ground keep an eyeball on it to make sure it’s not buried in snow this time of year,” Bouchar said. “If you or someone else is up on the roof, take a peek down to see if there is anything inside that could cause a block.”

Julia Bayly

Julia Bayly

Julia Bayly is a reporter at the Bangor Daily News with a regular bi-weekly column. Julia has been a freelance travel writer/photographer since 2000.