Plumbing Vent Definitions & Code FAQs

Q&A about plumbing vents & vent codes
Vent clearance distances, materials, routing,
size, noise, odors, repairs

Plumbing Vent Clearance Distance FAQs

What's the clearance distance between a plumbing vent and a clothes dryer vent

I am planning to install a Dryer Jack on my roof with 41" sheet aluminum vent pipe going from it to dryer.

There is a 1 1/2" plumbing vent pipe exiting the roof about a foot from where I need the Dryer Jack installed.

Is this within code? On 2020-09-21 by Anonymous

Reply by- plumbing vent clearance to dryer vent

Anon:

Both of these are exhaust devices;

We provide the major plumbing codes at PLUMBING VENT CODES - code sources

where you are welcome to download any of those PDF files to take a closer look for yourself.

You won't find an explicit building code statement about clearance between a plumbing vent and a clothes dryer vent on a roof.

I would consider that I don't want lint clogging the plumbing vent outlet.

Please see details at CLOTHES DRYER VENT CLEARANCES & TERMINATION

Here are example dryer vent specifications

An exhaust hood should cap the vent to keep rodents and insects from entering the home.

Do not use an exhaust hood with a magnetic latch.

Locate the vent such that there is no less than 12" (305mm) between the bottom of the exhaust vent hood and the ground surface

Locate the vent such that there is no less than 12" (305mm) between the nearest side of a dryer exhaust vent hood and an adjoining wall or building inside corner

No obstructions by snow, flowers, rocks, plants, fences, walls, air conditioner condenser/compressor units, etc.

For other readers, a "Dryer Jack" is a roof exhaust vent such as the model shown below, from DryerJack = https://dryerjack.com/

What's the minimum distance between a plumbing vent and a woodstove chimnmey vent?

In Louisiana is there a distance minimum code requirement between a stove vent and a plumbing vent on the roof exterior? - On 2020-11-12 by Aaron Hebert -

Reply by (mod) - code requirement between a stove vent and a plumbing vent on the roof exterior?

Aaron

Are we discussing a woodstove chimney?

If so, CHIMNEY HEIGHT & CLEARANCE CODES

Plumbing Vent Repair FAQs

How do we repair our plumbing vent stack that someone cut off and capped?

In this condo some idiot cut the stack at the roof so he could take out a wall and just capped it off. We need to hook it back up by code so we can sell the condo. It runs right through the kitchen. He wanted an open kitchen I guess.

Is it just a matter of connecting ABS from ceiling to floor? I can’t find a sketch of this issue. Any help would be great On 2020-06-18 by Shad sellers -

Reply by (mod) -

Shad

I would cut off the cap and - as this is probably plastic piping - glue on a plastic ABS coupling that's the right diameter for your vent pipe, and then a sufficient extension of ABS upwards above the roof.

See PLUMBING VENT REPAIR  where I made a similar repair to a broken-off ABS plumbing vent stack pipe.

My photo above shows how we used a plastic soda bottle for a temporary, emergency "repair" until I could make the proper one described in the article I just cited.

OR: Ask your plumber if a vacuum breaker vent can be installed and will be approved by local code officials. If so it'd save a lot of trouble and expense caused by the idiot .

Daniel

I put my plumbing vent tee in the wrong position - will the local building inspector accept it?

I’m in Minnesota. I tied a lav vent into a main stack vent and realized I put the tee so the sweep is facing downward. I know I should of put it the other way.

But just wondering if it’s legal so I don’t have to cut everything out. On 2020-02-11 by loven -

Reply by (mod) -

Final authority to answer that question is your local plumbing inspector.

But there's a reason for respecting the direction of plumbing vent elbows or tees: proper functioning of the system.

You should cut out the improper tee and replace it with one in the proper orientation.

See PLUMBING VENT TEE POSITION

Plumbing Vent Noise FAQs

Intermittent plumbing vent dripping sounds keep me from sleeping

I have been unable to sleep in bedroom For 1 year due to intermittent drip noises (sounds sometimes like it’s hitting water but no leak) but especially loud waterfall noise in wall where stack is. You can hear the same noise in both bathrooms also which are side to side and there is a stack there also .

I am On first floor in 9 story building built in 1969. Cast iron in the vertical stacks. Plumbers are clueless and say the noise is not normal. Louder than it should be. I don’t know where to turn. - On 2020-10-15 by Pt

Reply by (mod) -

PT

I agree that a dripping water sound can be very disturbing.

Take a look at

DRIPPING WATER SOUND SOURCES

for some suggestions. Let me know what you think by posting follow-up remarks there;

As it may prompt help from another reader I'll also copy your question to that page.

Toilet won't flush, just swirls. Could someone working on our chimney have caused the problem?

I have a lower level half bath where the toilet suddenly will not flush (water just swirls around). There is no blockage.

We just had some chimney work done - is there ANY chance that the chimney worker screwed up something with the vent pipe that could be causing this?

If so, what are we looking for when we get up on the roof? I am grasping at straws here - I cannot for the life of me see what could suddenly be causing this issue. Thanks in advance for any help! On 2019-05-09 by Marcia

Reply by (mod) -

Marcia

Absence of venting on the drain line can interfere with good drainage, but more-likely, when flushing a toilet, if the vent were blocked the toilet would flush but you'd hear a glub-glub sound at smaller nearby sink, shower, or tub traps.

I'd start by checking the water level in the toilet bowl and the water level in the tank at the end of a toilet tank re-fill cycle after flushing.

More detailed help is at TOILET FLUSHES POORLY

Plumbing Vent Odor or Smell FAQs

Is it legal to vent sewer pipes into the building attic?

New home construction, what is the code for venting all of the sewer pipes?

Is is legal to vent only to the attic or does it has to vent through the roof of other means to the outside?
Email address is "larrymiller@email.com" On 2020-08-02 by Larry Miller

Reply by (mod) - NO

Larry you NEVER vent just into the attic, never ever. The vent must go outside. The risks are odor, moisture, and even a methane gas explosion hazard.

Sewer smell when first using sink in a mobile home

@Anonymous,

how come I smell the sewer first thing in the morning when I brush my teeth

it hasn't always been like that maybe just the last couple of months

this is a 1969 mobile home unit. On 2018-05-21 by Anonymous

by (mod) - how come I smell the sewer first thing in the morning when I brush my teeth

I'd look for

- sulphur in the water supply first

then

- check for blocked or slow drains or a blocked vent pipe that is causing siphonage out of the sink trap

DIAGNOSTICS: before you brush your teeth lean down and sniff the sink trap / does it smell particularly bad?

Then when you first turn on water in the sink, lean down (don't bang your teeth into the faucet) and sniff the water stream - does it smell bad?

Plumbing Vent Routing FAQs

OK to conceal plumbing vent inside a concrete wall?

Vent can conceal concrete wall? what is the side effects if its conceal in concrete wall? which type of buildings i can install expose vent? is there any code requirements for expose or conceal? On 2017-05-19 by canerakcay

by (mod) -

Can.,

My opinion is that a plumbing vent could be concealed inside of a concrete wall just as it could be concealed inside of a framed wall.

However there are some differences.

• One is that if is a Plumbing Leak that needs repair it will be very difficult to access in a concrete wall.
• Two is unlike running event in a wood-framed wall, event pipe run inside of a concrete wall May interfere with the structural design of that well. Be sure to check with your engineer or architect

How high goes the plumbing vent pipe go above the sink before it can run horizontally?

How high above a planned new basement kitchen sink, below a window, does the 1 1/2" pvc vent pipe have to be...before running horizontally?

Currently this basement room is a laundry. Plan to move wash tub and washer and remodeling room to a small kitchen. Currently the wash or laundry tub was "T"ed into a vent pipe 66" from floor....is that HIGH enough? On 2017-12-26 by Roger

by (mod) - proper height for a basement and washer sink vent? - Above the flood rim

It should be above the flood rim of the sink

Is it OK if the plumbing vent is not perpendicular to the roof surface

The vent stack in the photo at the top of this page appears to be more or less perpendicular to the slope of the roof rather than vertical.

Is there a reason for this? On 2017-09-16 by Caper

by (mod) - Risk of roof leaks at plumbing vent flashing

Caper:

Thanks for the astute question.

No there is no valid reason for the angle shown in our photo, and worse, using a pre-fab stack vent boot flashing with the vent pipe at an angle as shown means that leaks are likely.

That simply was how the plumber cut the hole and routed the vent stack out through the roof.

She should have routed the vent vertically straight up through the sloped roof surface, not at the angle in this picture.

Plumbing vent boot flashing kits are designed to handle the sloped roof surface, as you'll notice in the photo: there's more metal on the "down slope" side of the boot flashing.

Watch out: a plumbing vent that is at too much of an angle with respect to the plumbing vent boot flashing may find leaks around the vent in conditions of heavy rain or melting snow or ice.

Does the roof vent pipe have to run at an angle or not?

Do you need to run the vent line at an angle or not? On 2018-05-01 by Anonymous

by (mod) -

If you mean does the vent pipe have to be at 90 degrees to the roof surface, NO. Straight up is fine.

 

Is it OK to have more than one plumbing vent up through the roof?

I'm creating an upstairs apartment. I'll be tying in to the downstairs building drain. It's distant, so I'm wondering if I should vent the upstairs separately. In other words, is it ok to have 2 roof vents? Thanks! On 2017-12-19 by Steve

by (mod) -

Yes I'd add a second roof vent, that's perfectly permissible.

 

Do I run the vent pipe or drain dead flat?

How about running from sink to tub and toilet then out roof?

Can you tie them in this way?

If so would I need to run pipe flat on the rafters or angel it just a little up to where it's going to vent out roof? On 2018-05-01 by Anonymous

by (mod) -

You generally don't want a line to be dead flat as condensate could accumlate and in a cold area, freeze.

Use the InspectApedia.com search box found above and find our article on DRAIN FIXTURE UNITS and you'll see how to calculate how many fixtures can go onto a single vent line depending on size and the amount of water each fixture uses.

 

Where do I connect the plumbing vent along the drain line?

My question is does the vent have to come off the end of the header line or can it be placed in between any of the fixtures and just cap the end. Having issues with accessibility on the end of the line.
I have a sink with a 2” vent tieing in at the bottom of the riser already as shown in the picture.
This main vent acts as a vent for
2 toilets
2 showers
3 sinks
1 tub
Let me know what you think. On 2019-12-16 by Tyler

Reply by (mod) - use "wet vent" code - link is here

Tyler


You can run a vent from other than one end of the drain but that will change fixture drain operation into "wet vents" for some fixtures

details are at DEFINITION of WET VENTED PLUMBING FIXTURES

Can we move a drain 2 ft. without causing a venting problem?

I’ve recently installed a basement shower where there used to be a bathtub.

We moved the drain approx 2 feet to accommodate this.

The drainage is now very poor on occasions but perfect at other times.

I’ve been told this may be a venting issue but the previous bathtub drain did not have this issue.

I put new tiles over this and can’t rip them up to access this. Is there any other possible fix?
Thanks 2018-03-25 by Jimmy Doyle -

by (mod) - moving a shower drain two feet - can still be vented OK

Moving a drain 2 ft ought not itself to cause a problem IF you maintained 1/8" to 1/4" per foot slope. If your drain slopes properly then I suspect the problem is a partial blockage or inadequate venting.

Can I move a vent stack pipe over horizontally?

In my back yard i have a vent pipe that runs straight down to the pipe that runs out to my alley. If i move this pipe does it have to straight up and down or can I elbow it to move it say 5 feet. - On 2019-08-04 by dave

Reply by (mod) -

If it's truly only a plumbing vent then you can probably move it over a bit. Look at the total vent line distance to be sure you're within code.

However if it's a sewer line clean-out access you may make cleaning the line more difficult in the future.

What do I do with the plumbing vent piping connections when I move the bathroom sink?

I'm moving a bathroom sink to opposite wall across the bathroom.

The current location is tied in with toilet to 3" sewer drain line and 2" vent pipe.

What do I do about venting the sink 1.5" pipe once I move the sink across the bathroom to opposite wall and tie into the 3" drain/sewer line. Also this project is upstairs - On 2020-07-04 by Joemomma

Reply by (mod) -

You would either route a vent line around in the wall / ceiling from the new location or you might be permitted to use an AAV or air admittance valve or Studor vent.

How do I vent a new sink if it's distant from existing plumbing vent line?

There is a commercial job that requires air vents no direct draining i need to put a hand sink and doublewash tub in can I connect those two drains into the 1 1/2 drain pipe from another wash tub already going into the air vent or do i have to bring a new 3 inch drain and air gap vent over to the new tubs? On 2018-05-02 by UNKNOWN CODE

by (mod) -

See if your local inspector will approve
An air admittance valve

see AIR ADMITTANCE VALVES AAVs - Studor Vents Explained

 

OK to put a drain vent under the sink on an outdoor grill-island ?

Can you plumb a drain vent under the sink on a outdoor grill island? On 2020-06-28 by tracymayo57@gmail.com

Reply by (mod) -

Sure, Tracy, but you may need to use an AAV or air admittance valve .

see DEFINITION of AIR ADMITTANCE VALVES / STUDOR VENTS

Plumbing Vent Size FAQs

How many fixtures can a 3-inch vent support?

How many Fixtures can you put on a 3" vent. What is the furthest distant you can be away from the vent? On 2017-05-04 by Tim

by (mod) - consider fixture type not just number, and look at this DFU table

Tim in the article PLUMBING VENT CODES, DEFINITIONS, TYPES see the

Tables of Plumbing Drain Pipe & Vent Pipe Sizes & Critical Distances to Plumbing Fixtures

Also see the calculations at PLUMBING DRAIN FIXTURE UNITS DFUs -

1 1/2" vent OK for a double vanity sink?

Can I rough in a double vanity with a 1 1/2 pipe On 2017-05-03 by Richie

by (mod) -

Richie,

See https://inspectapedia.com/plumbing/Plumbing_Vent_Definitions.php#Sizes where we discuss the size of vent pipe needed.

What was the sewer pipe diameter size in Alabama in 1992

What was the waste line size plumbing code in 1992 in a residential home in Alabama? On 2020-01-04 by Mickey

Reply by (mod) -

Mickey

I am so sorry that I cannot answer your question: there is no one "right answer"

as the necessary waste pipe diameter depends on the particular drain line being installed and what kind of plumbing fixtures it serves and the number of them.

The plumbing code has the installer calculate DFUs - drain waste vent fixture units DFUs = a number that then, combined with the length of run, determines the drain diameter needed.

Details are at PLUMBING DRAIN FIXTURE UNITS DFUs

You might check with your local building department to see if they have copies of the 1992 Alabama residential plumbing code on file;

I also found some older Alabama codes at the Internet Archive by searching for "History of Alabama Plumbing Code"

Plumbing inspector exam question: What type of material is prohibited for a vent stack?

What type of material is prohibited for a vent stack? Its on my Plumbing Inspector exam, and I cannot find the answer. I have been choosing Cast Iron pipe. - On 2019-12-16 by Anon -

Reply by (mod): lead pipe

Cast iron was permitted and often installed for plumbing vent piping in older buildings.

Also permitted: PVC, ABS, copper, and galvanized iron.

The ONLY plumbing vent material presently prohibited in most jurisdictions is lead pipe.