What a plumbing vent does and how it clogs
Every drain system needs air. The vent pipes run from your drains up through the roof so air can enter behind the water as it flows out. Without that air, the water drags against the pipe, drains run slowly and traps can be sucked dry.
Vents clog from the top. Leaves, a bird nest, a dead squirrel or a hard frost collar can close the opening. They can also clog from inside when grease or debris backs up into the vertical pipe. Either way, the result is a drain that behaves as if it were blocked.
Signs a vent could be the problem
A blocked vent and a blocked drain look alike. These clues point to the vent.
Gurgling from sinks, tubs or floor drains
Air is being pulled through the trap instead of the vent, so you hear it bubble.
Slow drains with no clog found
A cable clears nothing, yet water still moves slowly or in a rush.
Sewer smell indoors
A dry or siphoned trap lets drain gas into the room. It may also mean a cracked vent pipe.
Toilet that burps or fills with a hollow sound
Air pressure changes in the stack show up at the toilet first.
Vent problem or drain problem
| What you notice | More likely a vent | More likely a drain |
|---|---|---|
| Gurgling when a sink drains. | Yes, especially after the water has gone. | Possible if the sink is also slow. |
| One fixture slow, others fine. | Less likely. | Yes, a clog in that branch. |
| Several fixtures slow and gurgling. | Likely. | Possible in the main line. |
| Floor drain bubbles when toilet flushes. | Possible. | Likely a main line problem. |
| Problem began after a storm or nesting season. | Likely. | Less likely. |
How to check and clear a roof vent
Only try this from a stable, low-pitch roof in dry weather. If you are not comfortable on a ladder, skip to the call-a-plumber section.
Find the vent
Look for a 2 to 4 inch pipe that rises above the roof, usually near the bathrooms or kitchen. Many houses have more than one.
Look and remove debris
Shine a flashlight down. Pull out leaves, a nest or other material you can see with a gloved hand or a grabber.
Flush with a garden hose
Run water gently down the pipe. If it drains away, the vent is open. If it rises and stays, the blockage is deeper.
Test the fixtures
Back inside, run the sink, flush the toilet and listen. If the gurgle is gone, the vent was the cause.
Water rising in the vent or drains backing up?
Call the 24/7 line. A blocked vent with a stuck drain can bring sewage into the house.
DIY or call a plumber
Reasonable to try yourself
- Looking down a vent from a safe, low roof or a ladder
- Pulling out leaves or a nest you can reach by hand
- Rinsing a short vent with a garden hose
- Checking vent caps and covers after storms
Call a plumber
- Water rises in the vent pipe when you flush it
- A steep roof, a second story roof or ice on the surface
- A blockage you cannot reach with a hose
- A cracked vent pipe or missing flashing
- Sewage or floor drains backing up
Maple Heights housing and the vent stack
About 68 percent of the homes in Maple Heights were built before 1960, and the median year built is 1956, based on older survey data. Houses of that age often have a single vent stack serving the whole house, usually cast iron or older galvanized pipe.
An older stack can rust through below the roof or pull away at the flashing, and those problems look like a clog. If a plumber finds the vent open but the symptoms persist, the next step is a camera or an inspection of the stack. The Ohio Plumbing Code governs drainage and venting, so repairs should follow it.
Source type: State code index and survey dataWinter, frost and the vent opening
In cold weather, moisture from inside the house can freeze at the vent opening and form a collar of ice that narrows the pipe. If drains gurgle during a hard freeze and clear when it warms up, that is a clue. Do not chip ice from a roof edge or climb a frozen surface.
A plumber can check the opening safely and advise on whether the pipe size at the roof is appropriate. This is also a good time to check for a roof cap that traps leaves or a screen that has closed up.
If the vent is not the problem
Many gurgling drains turn out to be clogs in the drain line, not the vent. Our drain cleaning team cables the line and runs a camera when a clog keeps coming back. If a camera shows a bellied or cracked pipe, sewer inspection explains the next options.
Never pour chemical drain cleaner into a drain you suspect has a vent problem. The chemicals sit in the pipe and make the work more dangerous for whoever opens it.
Where we work
We take vent and drain calls across Maple Heights and in nearby Bedford Heights and Warrensville Heights. Tell us your address and which fixtures gurgle, and we will tell you what to expect.
Frequently asked questions
Yes. A toilet needs air behind the water to flush strongly, and a blocked vent can make it slow or noisy.
Yes, from a safe position on a low roof in dry weather. Use a gentle flow and stop if water rises in the pipe.
It is a plain open pipe, typically 2 to 4 inches wide, with no flame or exhaust collar. If you are unsure, do not guess, call a plumber.
It varies. Many older houses have one main stack and some have extra branch vents. A plumber can trace them.
The clog is probably in the drain line. Cable or camera work can find it.
Yes. You get a clear price before any work starts.