Believe it or not, there’s a pipe on your roof called a sewer vent (it’s also called a roof vent, plumbing vent, and vent stack). And when it gets clogged, it can be dangerous and even smelly.
Why? Because the sewer gas it’s supposed to vent stays in the house. Here are our instructions on how to eliminate the bad smell (and dangerous gas) coming into your home from a clogged roof vent.
What is a Sewer Vent or Roof Vent?
A roof vent or sewer vent is a vertical pipe (also called a stack) that allows (1) dangerous sewer gas to be eliminated from your house, and (2) air to enter your wastewater pipe system. It is a safety requirement for every building and one of the most important parts of your entire plumbing ecosystem.
Signs of a Clogged Sewer Vent
If you see (or smell) these signs, then your roof-top sewer vent might need to be cleared of a blockage. If that’s the case, it means air (and sewer gas) is not coming out of the roof vent as it should.
- Unusual noises coming from your drainpipes while water is flowing, such as loud gurgling. You can even have sounds like bubbling of water.
- Water that is flowing sluggishly in all the drains of your home likely means a clog in your sewer vent pipe. (If it’s just one drain, then the sewer vent on your roof isn’t the problem.)
- Unusual smells, like sewage, in the house or at drain fixtures.
How to Unclog a Sewer Vent on the Roof
If your sewer vent pipe on roof smells, it’s possible to clear the blockage without going on the roof.
But sometimes, it’s impossible to clear the clog from the branch drains, the main clean out, or when all the drains are slow or smell bad. In those cases, you’ll want to follow these instructions for clearing the sewer vent pipe from the roof.
1. Prepare to Work on Your Roof
- Safety comes first, always, when working on a roof.
- Only work in good weather and wear rubber-soled shoes to avoid slipping.
- If the roof is pitched, rent a ladder that hooks over the peak of the house (don’t use a ladder that can’t do this).
- For extra security, rent a safety belt and attach its free end to a fixed point on the roof, such as a chimney. This is especially important when working with an auger.
- Work while kneeling or sitting if the angle of the roof allows.
- Always have a helper on the ground to assist you and keep you from having to move up and down the ladder unnecessarily.
- Finally, if you have any fear of heights or are not comfortable working on the roof with power tools, call a professional plumber you trust to clear the roof vent pipe.
2. Use an Auger
- First, try doing this with a manual auger that has a cable at least as long as the distance from the roof to the bottom of the soil stack. Ask your rental supply center how long of an auger you need so you don’t have to go back and forth before you get it right.
- Feed the auger into the vent util it reaches the blockage, lock the handle in place, and rotate the auger clockwise.
- Feed in more coil as needed and stop occasionally to pull out any debris.
- Remove the auger, insert a garden hose, and flush the vent. The water will flow freely through the vent if the clog has been cleared.
- If the problem was that your drains smelled bad, you might need to wait a few days to determine if the smell has done away.
- If water backs up from the vent, you still have a clog. It’s time to bring out the big guns: rent a lightweight power auger.
- Feed the coil until the cutter head (at the end of the coil/cable) meets the blockage, then turn on the auger.
- Stop the power auger frequently and try to fish out the blockage rather than push it further down the pipe drain.
- Test with a hose (but have someone inside the house watch for overflowing fixtures, like a tub or toilet).
- If you still have a blockage, call your plumber.
3. Protect the Vent
- To prevent objects from falling into the roof vent, causing sluggish or bad smelling drains, add a cage to the end of the pipe. These are like the metal filters on a downspout.
- Cages are especially useful on flat roofs, where the vent is shorter and more exposed.
- Buy a metal cage the width of the vent at a hardware store and insert it into the top of the vent.
- An alternative to the cage is to cut a piece of metal screening slightly larger than the opening, bend it over the pipe and wire it to the vent.
4. Bonus: Expand the Top of the Vent Stack
Okay, this bonus step is for the serious DIYer with plumbing and roofing experience. Don’t do this unless you really know what you’re doing. For those who do, have at it!
- Increasing the diameter of the vent will help keep it from being blocked by ice in colder climates.
- As much a roofing project as a plumbing repair, it is a professional job that involves removing the flashing and adjacent shingles, removing a section of the old vent from inside the house, enlarging the hole in the roof, adding a wider vent and adapter, and applying new flashing and shingles.
- The entire assembly must be properly sealed to prevent leaking and water damage from your roof or the roof vent.
Final Thoughts: Sewer Vent Pipe on Roof Smells
There are several issues that can cause bad smells in your home. Below, you’ll find an article covering each one of them.
As you’ve learned, one of the main culprits is a blocked sewer vent pipe. Fortunately, you can clean it out from the roof. Just make sure you’re taking extra safety precautions and have the right tools, and assistance, to do this job. If not, we encourage you to call a plumber.
- 17 plumbing safety tips to prevent a DIY disaster
- Sewer lines: the essential homeowner’s guide
- Downspout cleanouts: step-by-step guide
- Why do I smell sewage in my house?
- Does homeowners insurance cover water damage?
- Common causes of water damage in the home
- Water Damage Page
- Sewer Repair Page
1-Tom-Plumber’s certified team of plumbers and drain technicians respond immediately to any emergency plumbing, drain cleaning, or water damage problem. We also handle the excavation of underground water lines and sewer main lines. Our immediate-response team is available every day and night of the year, even on holidays.