Plumbing vent FAQs:

Frequently asked questions & answers about plumbing vents: what is a plumbing vent, how do we define the types of plumbing vents, how is a plumbing vent installed, what is an air admittance valve, what is a wet-vented drain, what are direct-vented fixtures & what are the distances from plumbing fixtures to plumbing vent stacks?

This article series defines plumbing vent system terms, distances, and functions, and other specifications and code requirements. We explain how plumbing vents work on buildings, why plumbing vent piping is needed, and what happens to the building drains when the vent piping is not working.

More Plumbing Vent Questions & Answers, FAQs

These questions & answers about plumbing vents were posted originally

at PLUMBING VENT CODES, DEFINITIONS, TYPES - topic home.

This sketch of a plumbing stack vent illustdrating terms like wet vent, stack vent, horizontal branch vent and the slope required on the toilet waste line was provided courtesy of Carson Dunlop Associates, a Toronto home inspection, education & report writing tool company [carsondunlop.com].

On 2023-07-27 by InspectApedia Publisher - screens & wind vanes for plumbing vent rooftop vents prevent animals, debris, downdrafts

@Bill,

Yes, and in fact there are plumbing vent top opening caps specifically designed to turn down-wind to prevent wind down-drafts into the plumbing vent system: one of those would work for you.

Below I illustrate one of these, Camco's Cyclone plumbing vent top.

We cited this vent also in a reader Q&A discussion at SEWER GAS ODORS in COLD / WET WEATHER

Other roof vent guards that prevent trash or animals from entering the vent system include the Boot Guard shown below - sold by Best Materials

See this PLUMBING VENT BOOT GUARD INSTRUCTIONS [PDF] Best Materials,

On 2023-07-27 by Bill

I have a customer that has pine trees dropping needles into the vent pipe on the roof, causing it to become clogged up. Is it legal to put a 90’ elbow on the top to stop this from happening?

On 2023-07-27 by InspectApedia DF (mod)

@BC,

Please try again to post a photo.

On 2022-07-20 by BC

Hi. Thank you so much for providing this very useful website that I use often for understanding how things work in my home and how to approach repairs. I am trying to figure out whether the plumbing waste vent system is working properly.

I have a septic system and often experience septic odors in the toilet when it is clean and backup of toilet contents when toilet is used and flushed. It has been checked for clogs (none found)

. I’m attaching a photo of where the waste pipe comes through the attic and makes a 90 degree turn before running about 2 feet horizontally and then vertically about 15 inches out through the roof.

Should the waste stack go straight up through the roof without any turns? Also the waste stack has different pipe materials joined together (metal from crawl space and then ABS or other material added in attic for exiting through roof due to being mistakenly cut by roofers and later repaired.) Photo attached.

I plan to replace toilet anyway and will probably ask plumber to thoroughly check waste pipe system in that area to examine all pipe connections in crawl space as well as the sloe of the drain piAny other things I should be checking?

On 2018-01-02 1 by (mod) -

I don't quite get the question, Narendra, but yes often there is a direct connection between a sanitary waste pipe and the vent piping that extends up through the roof.

Wet vents - that carry waste down and vent gases upwards must be properly sized and routed as shown in the sketch here.

On 2018-01-02 by Narendra

can i convert sanitary pipe as vent in roof level or below level

On 2016-10-27 by (mod) -

Wind guards or caps on plumbing vents:

Nice question Anon. Indeed in some windy climates I see plumbers installing an upside-down elbow atop the plumbing vent stack above the roofline as an alternative to a wind cap - both are intended to reduce down-drafting. Whether or not you need to worry about downdrafts is building and site specific: roof shape, slope, orientation, and wind conditions.

If you see that other homes in the neighbourhood all have taken steps to deal with high winds and downdrafts, then your building probably needs the same. Check with local plumbers and with your building department too.

On 2016-10-27 by Anonymous

vent pipe through roof
should it be straight up and open
or have cover or elbow on top

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

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

On 2017-05-04 by Tim

How many Fixtures can you put on a 3" vent. What is the furthest distant you can be away from the vent?

On 2017-05-03 by (mod) re: Can I rough in a double vanity with a 1 1/2 pipe

Richie,

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

On 2017-05-03 by Richie

Can I rough in a double vanity with a 1 1/2 pipe

On 2017-05-03 by Tom

Question: I am finishing our DWV on my own after a plumber did the under slab work. The kitchen sink is about 20 It upstream and its AAV vented 2" drain passes a bathroom sink about 4 feet away from the trap of the bathroom sink. The code mentions only dry vented bathroom group fixtures fur use in wet venting the bathroom sink.

Can the kitchen sink drain be a wet vent for the bathroom sink? The other bathroom drains that might be wet vents are not accessible. So I am think the bathroom sink might have to have a dry vent. IPC governs.

On 2017-04-30 by David

What side of the trap does the sewer vent pipe get installed?

On 2017-04-21 by (mod) re: How far can a new toilet vent pipe be run and hooked into an existing air vevt pipe

Gary

At the start of PLUMBING VENT CODES, DEFINITIONS, TYPES click the live link

for DISTANCE: PLUMBING FIXTURE to VENT PIPE STACK to get a detailed answer;

About slope, 1/8" to 1/4" per foot

On 2017-04-21 by Gary

How far can a new toilet vent pipe be run and hooked into an existing air vevt pipe (in feet) horizontal or vertical and must they slant 1/4 in drop per foot?

On 2017-03-30 by (mod) re: separation distance between plumbing vent & gas boiler vent or skylight

Paul we have some information on these clearance distances found by searching InspectApedia for "chimney clearances" using the box just above.
That finds

FIRE CLEARANCES, METAL CHIMNEYS - though I don't think you'll see plumbing vents referred to in the codes on chimney distances.

You'll also want to see https://inspectapedia.com/chimneys/Chimney_Height_Codes_Specifications.php

Skylight distances to rooftop vents is in the model building codes
eg

Distance to Roof-Top Vents (CPC 906.2)
Operable skylights shall be located a minimum of 10 feet from all plumbing vents or the vent shall terminate 3 feet above the skylight. Operable skylights shall be a minimum of 3 feet from any environmental air vent (i.e. stove hood, bathroom fan, etc.)

Skylight distance to chimneys: I have not found a model code citation on this and am still looking; What does your local building inspector say she will accept? Probably 10 feet would be a minimum.

On 2017-03-30 by Paul

Roof penatrations. In the state of Massachusetts How much separation is required between a Gas boiler vent, a Wood burning fireplace chimney flu, a Plumbing vent pipe and a openable Skylite. ?

On 2017-03-22 by (mod) calculate the air volume passing through a 4" plumbing vent stack

Sameer


You'll want to do your own calculations by starting with some assumptions about the daily water usage at all of the fixtures connected to that vent.Here are a few clues that will help you out:

1. The seal of any fixture trap shall not be subjected to a pneumatic pressure differential of more than 1 inch of water column (249 Pa).
(The pressure differential will be a function of pipe diameter, water volume and flow rate)

2. With an atmospheric pressure of approximately 14.7 psi at sea level, there can be no more than plus or minus 0.036 psig difference present between both sides of the trap seal. 12 inches of water column equals 0.433 psig. 1 inch of water column equals 0.036 psig.

(Thanks to the Georgia (USA) Plumbing & Mechanical Association for the data above).

3. Your 4" diameter vent pipe can support up to 700 plumbing fixtures depending on other parameters - with an un-specified engineering assumption about the average wastewater volume and the maximum number of fixtures being drained at the same time.

Please be sure to r

eview PLUMBING DRAIN FIXTURE UNITS DFUs

PS: good luck on your exam.

On 2017-03-22 by Dr sameer s shastri

Need information on "how much air passes thr a 4" dia vent pipe n a day on an average?"

On 2017-03-20 by (mod) - how to add / improve plumbing venting in an older home

Slope sounds good.
Easiest would be running a vent from the crawl space outside as you described. Or you could run it in a wall and come out of the wall under the eaves if you don't continue up through the roof.

Or you could do a short AAV as you describe.
"Pass code" is a local determination. Some jurisdications don't automatically accept AAVs but approve them on request. What does your plumbing inspector say she'll accept?

On 2017-03-20 by Ruggerdeuce

Thanks for getting back to me so quick.

- The slope is better than a 0.5" per foot and the toilet is the only thing on the drain pipe that has a problem. The sink and tub drain fine.

- I'll run a camera down the cleanout and make sure there isn't a clog again but I really think it's a vent problem. I think the vacuum of the toilet is slowing the flushing and causing it not to flush well. You'd laugh if you could the mess. The vent pipe is a 2" steel pipe that runs though 6 feet of ABS to a cast 4" pipe. It then runs in the cast for four feet then into 4" ABS and to the toilet.

- "Can't add a new stack..." means I can't run one though the wall to the roof. I'd have to tear out the wall (a 2x4 wall so not much room for pipe) and put a new hole in the roof and that seems like more work than it's worth. The toilet plumbing is accessible in the crawlspace under the house and is really close to an outside wall.

I guess I could run a vent out the exterior wall to an exterior vent stack, I could run it up the side of the house to the roof but my wife will be way less than impressed with the look of a pipe running up the side of the house.

What I was thinking was pretty much the same scenario as above. But instead of running a vent stack to the top of the house, I wanted to run it up a few feet to get it above the toilet and cap it with a AAV. Then then toilet could vent and my wife wouldn't have to look at a pipe running up the side of the house. Do you think that would pass code?

Thanks again.

On 2017-03-19 by (mod) - diagnose repeated toilet clogging

Rug

A toilet line that clogs repeatedly is often traced to

- improper or inadequate slope - perhaps most-likely from your description

- inadequate venting maybe - e.g. causing slow drainage so that solids are not moving with liquids through the drain; indeed your vent sounds distant;

As you suggest, an AAV vacuum-breaker V-200 type vent installed closer to the toilet - search inspectApedia for AIR ADMITTANCE VALVES AAVs (use the search box just above) to see details, can work anywhere as long as it's 6" above the traps (in this case the toilet bowl water level);

Running the vent line outside: there are working vent systems that run outside of a building (though venting humid air say from a shower can cause freeze-up in cold climates), but I don't have a clear understanding of your layout; running a long pipe from a still-remote point from the toilet isn't going to help.

"Can't add a new stack..." does that mean you cannot get to the drain under the toilet nor into the walls near it? When I had a problem like that (it was an "inaccessible crawl space below a 1920's cottage) we cut into the crawl area through the bathroom floor, making a removable hatch; it's always informative to look into areas nobody's been able to see for decades.

- an obstructing intruding rim or other physical problem

If you're not sure you've correctly diagnosed the problem, I'd want to do that before going to a bit of trouble with the AAV - scoping the line with a sewer line camera can answer these questions.
- a clog that has never been fully cleared (try a rotary drain cleaner auger)

On 2017-03-19 by Ruggerdeuce

My house is really old and has obviously had verses additions and non-professional renovations over the last 100 years. I have a toilet that gets clogged all the time and gurgles when flushed (I'm thinking vent problem because I've looked for clogs). It drains to a 3" waste pipe.

It is currently being vented by a 2" pipe about twelve feet away. That is twice the distance of code.

I can't shorten the venting distance, add a larger vent pipe, or add a new vent stack to the venting system; it's just not feasible. The exterior wall is close. Can I run a pipe out of the crawl space to the exterior of the house and run the pipe vertically along the exterior of the house to a AAV?

The way I'm interpreting the code, the AAV needs to be 6"above the rim of the bowl of the toilet, running the pipe and AAV outside of the house is the only way I could cover the code. That is if I'm interpreting it correctly. Is this legal or is there a better way to deal with this situation? Thanks.

On 2017-03-15 by Steve

Once my 6 inch exhaust hood vent pipe is through the roof outside, how much higher does it need to go? Please email me the answer at Stevekimball777@gmail.com thx

On 2017-02-20 by (mod) - is plumbing venting required?

Yes by virtually every plumbing code in countries that have such regulations.

FYI, in areas where plumbing vents are not a usual part of plumbing systems, such as in our lab and office in the Mexican state of Guanajuato, people are accustomed to episodic blasts of smelly sewer gas burping up out of shower, sink and tub drains, particularly if those fixtures have gone un-used for a time.

Even before a trap is totally "dry" (thus back-venting sewer gases into the building) a partly-evaporated plumbing trap is more easily siphoned-dry by use of a nearby toilet.

On 2017-02-19 by Anonymous

Do u have to have to have vent pipe

On 2017-01-01 by (mod) - is it OK to change from cast iron to PVC vent piping?

Sure

On 2017-01-01 by Anonymous

I have leaking vent pipe that leaking it is 4' pipe cast iron can l change it with PVC pipe will it be OK in Massachusetts to do

I had a ventilation pipe put in my apartment around the first of October I can hear and feel air coming from the bottom and sometimes a terrible stench. Would my light headedness, headaches, running nose, dry cough etc. be coming from some gases in the apartment from the pipe.

The workers haven't came back to cap the floor seal with the same white ring up top at the ceiling. Really haven't been feeling too well and I have chronic heart problems. Can you let me know asap so if this air coming from the pipe is making me feel this way i can see if the guys can come back and correct the problem. Is it hazardous?

On 2016-09-16 by (mod) - How to find Canadian plumbing vent code specifications for Newfoundland

Anon: in Canada the model building codes established nationally - see http://www.nrc-cnrc.gc.ca/eng/solutions/advisory/codes_centre_index.html -- are adopted by the individual provinces and municipalities.

However both Newfoundland and Labrador have adopted the model codes only partially.

(The "codes" refer to the National Energy Code of Canada for Buildings (NECB), National Building Code of Canada (NBC), National Fire Code of Canada (NFC), and National Plumbing Code of Canada (NPC).) "

The National Plumbing Code of Canada 2015 (NPC), published by NRC and developed by the Canadian Commission on Building and Fire Codes, sets out technical provisions for the design and installation of new plumbing systems and also applies to the extension, alteration, renewal and repair of existing plumbing systems."

So I would start with the Canadian NPC on vent stack specifications but I'd also check with the local building department where you live as local adoptions may be different. You can get a copy of the Canadian plumbing code at 1-800-672-7990 Email: CONSTPubsales-Ventes@nrc-cnrc.gc.ca

Here are some typical plumbing vent stack diameter code texts

The minimum required diameter of stack vents and vent stacks shall be determined from thedeveloped length and the total of drainage fixture units connected thereto in accordance with Table 916.1 [or other table depending on what's adopted where you live], but in no case shall the diameter be less than one-half the diameter of the drain served or less than 11/4 inches (32 mm).

In freezing climates such as northern Canada the vent stack pipe needs to be larger to reduce the chances of becoming blocked by frost. E.g. for venting a toilet, you don't want a vent less than 2" and the main (or at least one) roof stack vent needs to be at least 3" immediately before passing through the roof (Winnipeg as example), 4" would be smart.

On 2016-09-16 by Anonymous

What is the building code requirement for a stack pipe vent diameter in Newfoundland?

On 2016-08-10 by (mod) - ICC Plumbing code on Plumbing Vent Flashings

I should have included this ICC model code paragraph too

904.3 Flashings. The juncture of each vent pipe with the roof line shall be made water tight by an approved flashing.

You can contact me by email using our page top or bottom CONTACT link and I'll be glad to send you a copy of the full ICC code on plumbing vents - that might help you avoid other trouble spots that you've not considered.

Daniel, I understand your frustration, but it's also frustrating for people who are aware of the various issues when being asked "just give me the answer" when a useful, safe, reliable answer requires at least a smidgen of actual information.

The other problem that you and I probably both encounter is that we sometimes are not asking exactly the right question, or we're not thinking of the problems that codes and standards people are considering.

I don't think you'll find "the number" for how far from a chimney a "pipe" (presuming you mean a plumbing vent stack or ?" can penetrate a roof. At least not a single number.

The issue is more likely to be that locating a roof penetration for a plumbing vent stack too close to a chimney makes it difficult to properly flash both the chimnney sides to the roof and the plumbing vent penetration through the roof. That in turn pretty-much guarantees a future of troublesome leaks. So a practical answer that's not "the magic number" depends on

- the location of the chimney on the roof

- the location of the plumbing vent on the roof

- the diameter of the plumbing vent and thus the size of the vent pipe flashing boot

- the roof slope

- the flashing design around the chimney

- the flashing design and product to be used at the plumbing vent

You'll want to put the vent far enough away from the chimney that you can flash both without risking future leaks because the flashing is a made-up kludge-job.

Codes focus on avoiding the inadvertent admission of sewer gases INTO the building through an operable window or air intake

904.5 Location of vent terminal. An open vent terminal from a drainage system shall not be located directly beneath any door, openable window, or other air intake opening of the building or of an adjacent building, and any such vent terminal shall not be within 10 feet (3048 mm) horizontally of such an opening unless it is at least 2 feet (610 mm) above the top of such opening.

904.6 Extension through the wall. Vent terminals extending through the wall shall terminate a minimum of 10 feet (3048 mm) from the lot line and 10 feet (3048 mm) above average ground level. Vent terminals shall not terminate under the overhang of a structure with soffit vents. Side wall vent terminals shall be protected to prevent birds or rodents from entering or blocking the vent opening.

Question: venting a back-flush or wall-hung toilet

(July 1, 2015) Antonio said:
Hi! Can i install a cheat vent on a hung toilet?

Reply:

A vacuum breaker vent, also referred to as an air admittance valve if permitted by your local building inspector, would need to be sized to handle the large toilet drain and would have to be installed where it's above the toilet outlet and able to obtain air.

In short, technically yes, with some inconvenience and with code approval. See this IPC citation:

905.1 Connection. All individual, branch and circuit vents shall connect to a vent stack, stack vent, air admittance valve or extend to the open air. 

Question: when to use a second through-roof plumbing vent stack

(July 21, 2015) Lyle Ruff said:

I'm 18 to 20 feet from the main stack. How far do I have to be before I have to run another vent through the roof?

Reply:

The maximum [developed] length of a plumbing vent in feet that you can use depends on

1. The diameter of the soil or waste stack pipe
2. The total number of fixture units being vented, where a "fixture unit" is a number determined by the type of fixture (toilet is more fixture units than a lav sink)

In my opinion, unless your vent piping is rather large diameter, say 6-8" you are already far enough to merit a separate roof vent stack. Take a look at the building layout, wall framing, wall locations, and ease of routing a line more or less straight-up from where you are. Compare that to the trouble and cost of routing through the building to a sufficiently-large stack vent 20 feet away.

See DISTANCE: vent piping be located from a plumbing fixture?

See PLUMBING DRAIN FIXTURE UNITS DFUs for an explanation of how DFUs are calculated and used

Question: rules about sharing a plumbing vent

(Aug 4, 2015) bob blanton said:
What are the rules about sharing the vent. I understand the wet venting rules, but if you're sharing the vent on the dry side, how do you know when you need to add another vertical pipe to the roof. Trying to avoid too many pipes coming out of the roof

Reply:

Good question and point, Bob and reasonable objective. I think the answer will lie in plumbing tables that discuss vent pipe diameter and number of fixutres.

Check tables 1 & 2 at PLUMBING VENT CODES, DEFINITIONS, TYPES to be safe.

Question: minimum roof vent height above the roof surface

Sept 30, 2015) Ed said:
What is the minimum clearance above a 2" vent above the roof?

Waste vent.

Reply:

Above the roof plumbing vent height: vent pipes should extend to outdoors above the building roof and should terminate vertically not less than 6" above the roof surface (nor more than 24") and must be at least 12" from any vertical surface (such as a nearby sidewall).

(UPC (i) 906.1 and 906.2). Note that there are other restrictions: for a roof that is also used as an occupied space, for example, the vent has to extend at least even feet above the surface and be secured with stays.

Details are at DEFINITION of a PLUMBING STACK VENT

Question: clarifying the chart of distances between plumbing fixture and vent stack

(Oct 2, 2015) Anonymous said:

Is the venting distance chart DRAIN & VENT SIZE & DISTANCES to FIXTURES for where the vent is in the wall off the drain pipe or where it terminates through roof horizontally so lets say
your vent pipe is 3" and 3' from sink and toilet in the wall but the vent terminates horizontally 12' away through roof does that still comply with the chart ?

Reply:

916.3 Developed length.

The developed length of individual, branch, circuit and relief vents shall be measured from the farthest point of vent connection to the drainage system to the point of connection to the vent stack, stack vent or termination outside of the building.

Question: More on distance between plumbing fixture and vent stack

(Oct 8, 2015) Anonymous said:

I have a plumbing vent that will exit through the first story roof, per the above chart I cannot tell if it will be "legal" due to two items.

An adjacent wall extends up the second story, where the attic louver vent is on one side (several feet above) and the other direction on the roof is a concentric vent (intake and exhaust about 3ft off roof surface) for the garage heater.

Will this vent be allowed in this location between the two items? If so what distance to either will be allowed, there is 11 feet clearance between the garage furnace and the adjacent wall. The chart above states 10ft to nearest window, but doesn't mention attic louver vents or furnace intake vent. Please advise.

Reply:

I think I'd need to see a photo or sketch to understand the question and to compare it with the distance and clearance tables in the model plumbing code.

For a complex situation it'd make sense also to ask for an opinion from your local plumbing inspector.

Question: convert a flat roof plumbing vent stack into a drain?

(Nov 12, 2015) Mike said:
Can a person turn a flat roof plumbing vent pipe into and drain

Reply:

Sometimes, Mike. See the discussion about Wet Vents in the

article DEFINITION of WET VENTED PLUMBING FIXTURES

Question: number of elbows, bends, curves in the vent pipe

(Dec 19, 2015) Cindy said:
Does a vent pipe have to come straight up or can it have several curves going out ?

And would it do ANY good if you put a vent straight from the septic tank ?

Reply:

Cindy

Vent piping may have elbows or "bends" - preferably 45 degree elbows not 90s

Venting straight up from the septic tank is not normally required. If you're thinking of that I speculate that your system may have a clogging or field problem

Question: connection of trap arm to vent pipe for a toilet

(Dec 22, 2015) Felix said:
should the trap arm need to be in a straight pipe segment when locating the vent pipe for a water closet?

Reply:

(Dec 22, 2015) (mod) said:
Felix I'm not sure I've got the question clearly in mind, but generally a P-trap connects to a vertical or horizontal (sloped) drain.

Question: vent height requirement for basement sewage lift pump

(Jan 19, 2016) Dan said:
I am installing a sewer lift in a basement. How high does to code require the vent to be?

Reply:

Dan
Unless your local building inspector approved your use of a vaccum-breaker "cheater vent" such as a V-200, the vent is directed above the building roof line.

Question: minimum vent size requirement for a specific number of fixtures

(Feb 3, 2016) Anonymous said:

What is the minimum size of vent needed for 3 W/C and 4 lavs/1 kitchen and 1 laundry tub

Reply:

See the table at DRAIN & VENT SIZE & DISTANCES to FIXTURES

Question: Using 90's to drain a standard toilet?

(Feb 5, 2016) Ken Densmore said:

Can 2 immediate 3 inch 90's be used draining a standard toilet?

Reply: 90's are not recommended

A 90 should not be used in most drain pipe locations and not at all in toilet drain piping: use a wye or a 45.

The 90's will tend to cause clogging.

(Feb 11, 2016) Riggs said:

==> Ken : You cannot lay down a 90 greater than 2" in size horizontally. Since the smallest toilet drain pipe should be 3" you should not do that.

Question:

(Feb 11, 2016) Zack in TX said:

I am connecting a toilet line into a 4" vented horizontal branch along a beam. I want to jump up to the joist space with a 4x3 wye rolled up and 45 to horizontal again and then run 3" about 8 feet to a 90 ell up to the flange. Is this ok? Does this 3" horizontal line need venting? I think not since the trap is in the toilet and fills itself when done so it wont siphon right?

Reply:

See DISTANCE: PLUMBING FIXTURE to VENT PIPE STACK

Question: does code require venting of sanitary piping lines? (sewage or blackwater or building drains)

(Mar 1, 2016) K.O.B. said:
Are sanitary lines supposed to be vented by code?

Reply:

Yes

See plumbing code citations on plumbing vents found

at PLUMBING VENT CODES, DEFINITIONS, TYPES

Question: distance between horizontal vent run and trap on plumbing fixture or fixture itself?

(Mar 20, 2016) Neil hershey said:

Distance between horz vent run from trap on ficture or ficture it self

Reply:

[Click to Enlarge Any Image] This sketch of distances, provided courtesy of Carson Dunlop Associates, a Toronto home inspection and education company.

Question: elbows & bends in vent piping

(Apr 13, 2016) are elbows allowed in vent stacks and piping? - anon

Reply:

(Apr 13, 2016) (mod) said:
Bends are allowed, though a 45 is better than a 90

Question: venting six pedicure sinks over 25 ft. span

(May 20, 2016) Michael said:
If tying in to 3in trunk like e to add 6 pedicure sinks on a 25ft span how far is my vent allowed ,do I need more than 1 relief vent

Reply:

At PLUMBING VENT CODES, DEFINITIONS, TYPES we point out that there are distance limitations between a plumbing fixture trap and the nearby vertical vent stack.

Question: difference between an aerator and a de-aerator

(June 20, 2016) Biswajit said:
What is the difference between de-aerator and aerator?

Reply:

Aerators add air whiile de-aerators remove air.

You'll find an aerator on the tip of many sink faucets, adding fine air bubbles and preventing the faucet from splashing.

You'll find de-aerators in many applications where air needs to be removed from a liquid, such as

- deaerator on some well piping or water supply systems

- deaerator on hydronic heating systems

Question: cut and cap waste pipe with a "switch" to avoid foul air entering a room

(June 20, 2016) Lallubhai Mistry said:
Is it possible to cut short the waste pipe inside to say toilet cistern level cap it with some short of switch so foul air does not stay in the room?

Reply:

If you don't vent a fixture at all it won't drain well and you'll siphon water from the fixture trap, leading to smelly anbd possibly dangerous sewer gases in the building.

But vacuum-breaker vents may ba permitted by your local plumbing inspector in some cases.

See ISLAND SINK PLUMBING VENTS

Question: adding a toilet, connecting to existing vent stack

(June 30, 2016) ron said:

If adding a toilet on the second floor, can it be connected to the vent stack if placed within 12" from the stack

Reply:

Please see DISTANCE: PLUMBING FIXTURE to VENT PIPE STACK

Question: toilet drain size vs. vent size distance: drain gurgles or burps

(July 6, 2016) Léon said:
My toilet drain to main is 4". The vent is 3" and is approximately 8' away from toilet clean out. Sometimes when I flushing, the bath tub drain will gurgle/burp. Would moving my vent closer on the toilet run fix this?

(July 6, 2016) Anonymous said:
My bathtub and kitchen drains are approx 16' apart 1 1/2"; they are tie in to the main at a TeeY approximately mid distance. The vent is a 1 1/2" and is close to the tub the kitchen sink drain distance to the actual vent is approximately 12'. Occasionally when the tub drains the kitchen sink gurgles/burps. Would tie in another vent closer to the kitchen sink fix this?

Reply:

Leon, if the drain has always gurgled I suspect the venting is inadequate or blocked since installation. If the gurgling developed later I suspect a clogged drain or failing septic system.

Anon: both of you will want to see the diagnosis and repair suggestions at

PLUMBING DRAIN NOISE DIAGNOSIS

Question: venting rerqured for bathtub

(July 6, 2016) Léon said:
Does the bathtub drain require a vent from it's drain to vent stack or is the overflow/vent sufficient?

Reply:

Yes the bath tub requires a vent. The overflow won't vent adequately, risks trap siphonage and sewer gas odors in the bathroom, and will gurgle annoyingly when the tub is draining.

Question:

(July 6, 2016) Léon said:
Teeing off drain lines to branch into my vent stack; is there a requirement for elevation above drain lines before an elbow is inserted to tie in to the vent run.

In other words is a Tee in the drain line with a 2" elevation above it to a 90deg and tie in to another elbow off of the top of the vent run acceptable? (the vent run is sloped to drain before the stack rises) Thanks

Reply:

Leon: take a look at the vent stack sketches

at PLUMBING VENT CODES, DEFINITIONS, TYPES; you'll see some tees coming off of the horizontal drain.

Question: distance between plumbing vent roof penetration and chimneys

2016/08/10 Daniel said:
how far from chimney and valleys can pipe penetrate roof

please sombody tell me.ive been searching for answer for hours but all i get is how to fix and repair everything under the sun.i just need some numbers

Reply: avoid roof leaks by overlapping or crowded roof penetration elements that prevent good flashing installation

Daniel, I understand your frustration, but it's also frustrating for people who are aware of the various issues when being asked "just give me the answer" when a useful, safe, reliable answer requires at least a smidgen of actual information.

The other problem that you and I probably both encounter is that we sometimes are not asking exactly the right question, or we're not thinking of the problems that codes and standards people are considering.

I don't think you'll find "the number" for how far from a chimney a "pipe" (presuming you mean a plumbing vent stack or ?" can penetrate a roof. At least not a single number.

The issue is more likely to be that locating a roof penetration for a plumbing vent stack too close to a chimney makes it difficult to properly flash both the chimnney sides to the roof and the plumbing vent penetration through the roof. That in turn pretty-much guarantees a future of troublesome leaks. So a practical answer that's not "the magic number" depends on

- the location of the chimney on the roof
- the location of the plumbing vent on the roof
- the diameter of the plumbing vent and thus the size of the vent pipe flashing boot
- the roof slope
- the flashing design around the chimney
- the flashing design and product to be used at the plumbing vent
- possible (though I suspect unlikely) downdrafts caused by wind impacting a nearby chimney side

You'll want to put the vent far enough away from the chimney that you can flash both without risking future leaks because the flashing is a made-up kludge-job.

Codes focus on avoiding the inadvertent admission of sewer gases INTO the building through an operable window or air intake

...

Continue reading  at PLUMBING VENT CODES, DEFINITIONS, TYPES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see PLUMBING VENT FAQs-3 - more-recent questions and answers about plumbing vent installation, codes, troubleshooting

Or see these

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