Q&A for How to Vent Plumbing

Yes, every plumbing fixture should have one. Vents introduce air into your sewer system, which helps liquids flow smoothly through your pipes.

Yes, they usually do. There are main vent lines that exit out the roof of a building, with other fixtures tying into these main lines.

It really depends on the vent. For example, if you were talking about a vent for your main sewer line in NYC, it'd get installed behind the house trap.

I do not see how. A vent is there to let air into the drain pipe as water leaves, and no air can run through the trap. If air did somehow run through the trap, you'd no longer have a trap.

Your toilet should fill with clean water after it is flushed. If it flushes fine, then it sounds like it is vented just fine. If the line from your septic goes to the roof, then your system is vented fine.

That is best, as you need to flash (water seal) around the vent stack to keep water from penetrating into the house. You can flash after the roofing is on, but this is unwise.

The vent does not have to be at the tank. You can have a pipe run from the drain pipes within your home straight to the roof (typically your highest drain, like second floor shower, in my case). All the drain needs is the ability to move air while water is moving through the pipes.

Check with your city/county. They normally have specified minimum sizes depending on the number of people using it on a regular basis.

Your sink drain will connect to the pipe going up through your roof. As long as the sink drain connects to the main drain of the building within a few feet, then it is vented. If the drain travels to the basement and connects to the main drain 8 feet or further away, then you need to run a vent for that sink drain. You could also install an indoor vent under the sink if needed.

Yes, two feet from the main drain is the maximum distance allowed for proper function. As long as your toilet is draining in the same drain pipe no more than two feet from where the drain goes down (usually at the tee), you're fine.

Chances are that it IS vented. It might be using a "wet vent" system where the drain pipe is also the vent pipe.

Generally, no. 1-1/2" is normally the minimum size for venting, and it may need to be even larger depending on the number and type of fixtures.

No more than 10" is recommended. But certain municipalities have specific requirements in the building codes. Just make sure to use either 2 45s or a long sweep 90 at the bends.

I've never seen it done. The odor and gases that travel through the vent will be drafted to the roof naturally. No need to install anything on the plumbing vent line on the roof. They do make a spinning fan-like object that can be placed on the vent. As the air leaves the vent when a toilet is flushed the device will begin to spin from the force of the air that is being vented. It will not spin unless the vent is being used.

Yes. It still needs to be vented in order to drain. Make sure the 3 inch pipe is run to the main waste pipe line.

It is most likely the toilet itself as there is usually a sink nearby which would run to the same drain; the drain is either wet or dry vent. It sounds like either the toilet itself has buildup or the drain from the toilet to the main line is clogged. Try to snake and see if that helps. If not, I'd replace the toilet.

A vent pipe is usually just an extension of your main waste line. The waste line gets run up your home with drains and toilets being tee'd into it. The waste line then continues up to the roof so every drain connected to that waste line is vented.

Yes, that's called a wet vent. Check with local codes to make sure the distance meets code.

You don't vent the water connections; you only vent the drain. On a washing machine, you use an open venting drain. The drain line just gets placed inside a 1.5 inch pipe, and the bottom of that pipe (going up the wall) has a trap on it to prevent odors and gases from escaping.

Under certain circumstances, a bend will cause water to leak or possibly fill with pressure and explode. If you spot a bend on a vent line, you should probably call a plumber.

The drain line must be no less than 1/4" per foot. Your current drain is only good for 24 feet. To fix this issue, your drain must be run on more of an angle/slope. To help prevent clogging, remove food and other particles from dishes before placing them in the dishwasher. This will eliminate most of the clogging issue without having to change your drain pipe slope.

Sounds like the waste line from the toilet's new location to the main waste line is too far. This will cause solids to drag and get stuck in the waste line, eventually making their way to the main waste line, but most likely causing a clog over time. The waste line from the toilet to the main can not be more than 2 feet.

You will need a 1.5" dry vent pipe minimum. You will also need an above water closet and 2" pipe from toilet to water closet.