What is venting?
You have a plumbing project on the go, and someone asks you "Where's the Vent?", or tells you, "that fixture is S-trapped". What does this mean? What is a vent and why do you need one?
Everyone knows that every toilet, bathtub, sink, shower, etc. will have a drain to carry the water away to sewage treatment, or your septic. But not everyone knows that they ALL also need to be vented.
Whether you're putting in a tub, toilet, sink, or floor drain, they all need a plumbing vent on the drain to make it work properly. If there is no vent, a number of problems may occur:
- The fixture without a vent may drain slowly
- The drain will likely make gurgling noises
- The water in the trap could siphon out, resulting in a potent sewer smell
- The smell emitted from an unsealed trap (Methane Gas) poses a health risk
Installing a vent will solve all of these issues and the building code also requires it.
There are many wrong ways to put in a plumbing vent and the building code is very specific to how it should be installed. If plumbing is not your forte, you should definitely call a plumber in your local area. (Guelph Plumber)
The size of the vent is very important. Many sinks only require a 1 1/4" pipe
but that size is increasingly uncommon and most plumbers run 1 1/2" abs pipe for a vent on every fixture since the price for 1 1/2" is actually cheaper. If you are dry venting every fixture, then you can nearly always use a 1 1/2" pipe. However, if you put an individual vent on every fixture, you are doing more work than you really need to do. Often times you can combine vents between two fixtures using a wet vent. (Learn more about this at What is Wet Venting?) This makes venting more complicated. As an example, a drain from a bathroom sink can also serve the dual purpose of acting as a vent for a toilet. But in doing so needs to increase in size from 1 1/2" to 2". And the connection for the sink vent must be a continuous vent.
The location of the vent on the drain also matters. For example on a 1 1/2" sink drain the vent can not be located more than 5ft away from the trap and the pipe between the trap and the vent can not have bends in excess of 135 degrees. The rules for siphonic fixtures such as a toilet differ. You can have the vent 10ft away and have 225 degrees before the vent. But these only apply if the fall of the pipe doesn't exceed the diameter of the drain pipe.
There are other rules that also apply to venting. You may connect the vents together from different fixtures, as long as they connect together above the flood level rim of the lowest fixture. The vents must also continually slope upwards (may not have low spots or dips) and eventually must terminate out the roof of the building through a flashing with a 3" terminal.
Sometimes there are situations where it is seemingly impossible or at least
impractical to get a vent upwards to another usable vent location or to the roof and yet a vent is still required. There is a product meant specifically for this situation called an Air Admittance Valve (or cheater vent for slang). This is a mechanical vent and meant only to be used when a natural vent will not work. It is a replacement for a vent and also has rules of use, specified in the building code.
Although home owners are legally permitted to work on the plumbing in their own homes, often times it is in their best interest to call a professional if they are not confident that they are doing it correctly. Venting and plumbing your house incorrectly can be quite costly and damaging. For a plumber in Guelph contact 519-780-0088 or visit www.jaytechplumbing.com/contact
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May 7th, 2011 - 22:40
I appreciate, cause I found just what I was looking for. You’ve ended my 4 day long hunt! God Bless you man. Have a great day. Bye
May 27th, 2011 - 23:21
I really like your blog.. very nice colors & theme. Did you make this website yourself or did you hire someone to do it for you? Plz respond as I’m looking to create my own blog and would like to know where u got this from. thank you
May 28th, 2011 - 09:01
I used a template and redid it to look the way that I wanted. Thank you for the comments.
January 26th, 2012 - 06:58
Very detailed blog, Helped me alot with some research i’m doing at the moment. Thankyou very much!
April 14th, 2012 - 06:35
Plumbing vents consist of pipe lines which connect to the plumbing to carry air away from the system. Commonly, multiple venting pipes join together and connect to a single pipe which pierces the roof or runs up the side of a structure to release the vented air.
May 20th, 2012 - 14:30
I was wondering if i could put a vent before my shower trap and run it to my 3″ main stack
May 22nd, 2012 - 08:06
Hey Matt. You can run it too the stack but it must be vented within 5ft and downstream of the trap. I hope that helps, cheers.
August 8th, 2012 - 18:48
hi..i need your help guys..coz i need to put an exhaust fan on my kitchen and when i phone electrician they told me it\’s carpenter\’s job, when i phone carpenter they said it\’s a plumber\’s job. when i phone plumber they said it\’s an electrician\’s job? oooh.. i dont know..pls. help me!
August 10th, 2012 - 16:37
In my experience that falls under the duties of the hvac contractor. The v in hvac stands for ventilation.
I hope this helps.
Mike.
September 2nd, 2012 - 18:27
Your illustration with the simk is great but wherr would I enter a shower drain that is a pan only, just straight into the stack?
October 2nd, 2012 - 08:18
Hey Tom. If the sink drain comes off on the horizontal instead of vertical as shown in the drawing then you could tie in a shower drain to that without an extra vent. But the shower needs to be within 5ft of the drain otherwise a separate vent will be needed anyway. Is this helpful?
October 30th, 2012 - 10:35
Thanks for all the help! I’m working on my bathroom installing some things and when I called plumbers in Salt Lake City Utah to ask them for help they asked me to look for a vent. I thought they meant the fan vent but now this all makes sense. Thanks!
November 6th, 2012 - 06:45
Thanks for your blog. I just landed up in your blog and I really appreciate your blog. It is full of resourceful information.
November 26th, 2012 - 10:08
Hello,
My house was build in 1948 without a plumbing air vent. I have owned it for 21 years.
2 or 3 times a year, the Septic Tank gets an air lock and the toilet stops draining correctly. It starts with when the washer drains, bubbles can be heard in the bath tub. Then the water level in the toilet starts going down when the washing machine drains. Then the toilet starts not flushing, the water in the bowl just slowly swirls around and empties so slow, no waste material goes down?
For years, I used to go out and using a pry bar, lift one edge of the heavy concrete septic tank lid. This breaks the air lock in the septic tank with a whoosing sound and everything is fine again. Weird but one time a neighbor lifted the lid right off and the water in the septic tank rushed upwards from the air lock, then the level dropped back where it belongs.
This often happens when winter comes up here in northern Canada. Extreme cold weather, then the weather warms up, then it turns cold again. The trouble is this time, the septic tank lid is frozen on and I can’t budge it? I have become to old and crippled a woman to struggle with it.
Three questions as we have no plumbers up here in the bush country who can come out. One plumber on the phone said to pour boiling water around the approx 4 inch thick X 30 inch concrete lid to defrost it so I can maybe lift it a bit but I am afraid to do that as then it will be frozen on even tighter afterwards? (1) How else can I defrost it so I can lift it a bit to get rid of the air lock? (2) Is there anyway in side the house to get rid of the air lock or stop it from happening, such as a temporary solution as no plumber or anyone to start running an air vent up through the roof? (3) Could a person chip a tiny piece of the cement lid out, say on the side and leave a small piece of pipe or something sticking out to prevent the air lock or would the water in the tank then freeze?
25 below and getting colder soon. Winter temperatures to 40 below up here.
December 17th, 2012 - 16:51
Thanks for the question Gayle. You are definitely emphasizing the need for proper venting. I’m not fully convinced that venting is the only problem here however. It seems like you also have a partial blockage in your drain. One thing you could try though is letting some air into (or out of) the drainage system. Try disconnecting a trap from under a sink (preferably the highest one) and flush the toilet. If the toilet flushes fine without the trap on, then I think it would be safe to say that it’s a vent issue. If not, then you’ll have to clean out the blockage.
Let me know the results.
Thanks,
Mike.
February 8th, 2013 - 21:07
I am really enjoying this article! I am wanting to find some plumbers in Guelph Ontario. Do you know of any?
February 13th, 2013 - 15:14
Hey Marie. We are actually plumbers in Guelph Ontario. Follow that link to reach our home page or call us at 519-780-0088. Thanks.
February 18th, 2013 - 12:11
Very great information. I have a question regarding a basement bathroom remodel. Thebathroom was roughed in when the property was built in 2006. The previous owner did install all the fixtures to complete it. (Tub shower combo, toilet and sink) I have since removed all of those and am moving the sink supply lines and drain line (they are in the wall), and moving the shower drain for a better use of the space. This is a concrete slab and I have already had the concrete cut to make way for the new drain line. The shower drain will be moved 7 feet and the sink about 4 feet. Do I need to install any new vents since I am moving the drains? And when I connect to the old shower drain, should I use a 45% elbow ? I know that I need a 1/4″ fall per foot for the slope. At 7 feet that would be 1 3/4″. Is a p-trap necessary on the new length of shower drain? Thanks for your help.
February 21st, 2013 - 08:38
Hey Tammy. Thanks for the question. To answer your questions the best I can without seeing the situation, I would just have to say that the shower as well as the sink need to be vented at no longer than 5ft from the trap. Therefore, if the shower is 7ft or longer to the vent connection, then you’ll have to put one in for sure. You’ll have to measure the sink drain to see if that one works. As for the fittings, 45′s are recommended underground but not nescessary. A 90 would also work.
Hope this helps.
February 22nd, 2013 - 16:45
WONDERING IF I NEED 2 TRAPS FROM THE SHOWER DRAIN THE WATER DRAINS SLOW THERES A TRAP RIGHT BELOW THE DRAIN AND 2 FEET FROM THAT THERES A TRAP THAT S IN THE SEWER LINE CAN I JUST RUN A 90 AT THE SHOWER DRAIN AND LEAVE THE ONE THAT AT THE SEWER LINE AND GET NO GAS BACKUP
February 25th, 2013 - 16:15
Hey David. There should only be 1 trap on your shower. If you eliminate one it should be the further one and keep the one under the shower.
Cheers.
February 27th, 2013 - 03:59
HI David,
I am in Australia. I have a house built in the 80s. Bathroom has 2 vanity sinks, a toilet and a shower and a floor drain/vent. I have a septic system. At certain times the bathroom smells. I have tried having the septic emptied, I have tried natural enzymes, hot water and bleach. Some of them work temporarily but none always. Right after the septic was cleaned out the smell still came. I think, but not sure rain brings it too. I cannot figure out what it is since is comes and goes, but mostly is there. Some days there is no smell and I do not know why.
Help!!! Thanks. Lynne
February 27th, 2013 - 15:30
Hi Lynn. A common problem is floor drain traps drying out over time if there is no source of water priming it regularly. Can you tell if there is any water in the floor drain trap? Perhaps top it up anyway and see if the smell dissipates. If that’s not the solution then let me know and we can keep moving forward.
Mike.
March 25th, 2013 - 15:20
Hi David ,
I bought a townhouse 3 years ago . When we shower on the second floor the drain in the kitchen starts gurgling. ( on the first floor) I have had friends and plumber come her twice spending close to 1000.00 .
When taking baths and you release the water the kitchen floods out from the sink, if you slowly release the water it doesn’t flood . I was told by the plumber that both bathrooms need to be vented and it would stop.
Is that true ? And if so how much would that cost.
Best Regards
Joseph W.Finch,Jr.
March 26th, 2013 - 07:50
It is true that every fixture needs to be vented. However it sounds like you have a half plugged drain in this case. So when you let a large amount of water into your drain it can’t keep up and it comes out of your kitchen. When you drain it slowly then it can keep up. You need to get a sewer snake down the drain and clear out the plug.
Thanks for the question.
Mike.
March 28th, 2013 - 00:38
I have a fish tank on the first floor, and the filter is in the basement.
The tank is two hundred gallons, I drilled the back of the tank with an 1″and1/4 on both ends.
They are both connected like a Y ..
It gurgles and makes noise
Do I need to put a vent pipe in there,& if so where does it go..
March 28th, 2013 - 16:00
Hmm, that’s a tough one Arthur. First time fish tank question for me haha. I would say that if they are both drawing in water to supply the pump then make sure they both are drawing water only (no air) and make sure the pump is primed well. (no air trapped at the pump). It shouldn’t need to be vented. Maybe a fish expert could chime in here if I’m wrong on this…
April 5th, 2013 - 07:11
I just love it! very interesting topic, I hope the incoming comments and suggestion are equally positive. Thanks for sharing information that is actually helpful.
April 6th, 2013 - 09:25
concerning the aquarium gurgling problem. If I understood correctly,
he mentioned the suction side but not the supply side of the system. I wonder if it’s full of water, if not maybe this is where the noise is coming from…like a straw in an empty cup noise?
April 6th, 2013 - 09:28
I forgot to mention that a vent is NOT needed in an aquarium pump system, it is actually best if air is not admitted into the system.
April 19th, 2013 - 18:40
Got lucky and stumbled onto your blog — I am replacing an air vent in small bathroom. After cutting hole I found 1 1/2 ABS pipe just above ceiling preventing install of new fan. I figured out it was an air vent. The vent apparently is used for multiple purposes as it also goes to laundry room. There is a 1/2″ pvc pipe feeding into the ABS pipe that looks like it goes to water softener in garage. My question is, can I lift the portion of the vent over the new fan by cutting and inserting a couple of 45 degree fittings? It would look something like ____/—————\___________ The lift would run about 2 feet long and 6 inches high. Thanks
April 22nd, 2013 - 15:21
Good question Stan, and that’s a beautiful drawing! The code actually doesn’t allow for this because there is always a bit of condensation that can build up in vents and if you have a low spot in the pipe somewhere, then it will trap water and won’t be functional anymore… air won’t flow through. If there happens to be nowhere that traps water still after you do this however, then no problem.
May 2nd, 2013 - 12:32
Hi Mike
Great blog….. I am interested in adding a washing machine to the basement apartment in my house here in Ontario. Currently, I would like to use a 2″ drain that is on the side of the apartment where the laundry would be best located. This branch currently drains two fixtures: a 1.5″ Kitchen sink in the basement apartment that is vented, and a washing machine with 2″ drain running down from my second floor. The vent for the basement kitchen sink is 1.5 ” pipe within 5′ of the trap and this vent travels up to a separate toilet stack on the second floor and joins in above that 2nd floor bathroom. Can I use this 2″ drain and the 1.5″ vent to drain and vent the planned basement washer?
thanks
Drew
May 17th, 2013 - 08:09
Hi Drew.
You described this well enough for me to safely say that yes you can use both the 2″ drain and the 1 1/2″ vent. Just make sure that you tie the vent in at least 40″ above the floor.
Cheers.
May 11th, 2013 - 11:56
Hey there. Just wanted to say, I have found your website extremely helpful. Im a first year in Alberta and while Ive worked on plumbing (obviously lol) my experience has only been bits and pieces, some groundworks here, pex installation there, fixtures here, between sites. Very hard to put it all together, and journeyman seem to forget that first years DONT really know much. Haha. Anywho, looking forward to exploring your website and learning more. Thanks so much.
May 17th, 2013 - 08:20
Thanks Kate. I actually know a great company in Alberta… Blackstone Mechanical. All the best with your career!
May 14th, 2013 - 07:50
Hi there.
I have a Simer Utility Sink pump(new). Instructions say it does not require a vent. The first time I applied water from the sink it pumped it out fine. After that I am unable to get it to pump water. Got a second new pump thinking that the other was faulty. Still will not pump water out. The pipe layout is as follows. Sink-trap- 12\” pipe (1 1/2) to pump. Pipe (1 1/4) 12\”to wall with a clapper valve in it (supplied). 90 deg turn horizontal run for 24\”. 90 deg turn vertical run for 8 feet. Then across ceil to plumbing waste line. (Horizontal run for 10 feet). The instructions state the pump will lift eleven feet. Co. technicians can\’t help.
Any Idea what I can do?
May 17th, 2013 - 08:24
Is the pump sitting in a sealed tank? If so, it does need a vent to work properly… When water is removed then something needs to take its place to prevent a vacuum from occurring. Normally this is just threaded into the lid or top of the tank. Does this make sense in your application?
May 17th, 2013 - 13:15
Thankyou for replying. No it is not in a sealed tank. The water runs directly into the pump. The company states it does not need venting.
May 17th, 2013 - 13:31
Can you send me a make and model of the pump?
May 17th, 2013 - 13:50
Make – Simer
Model – 2935B Utility Sink Pump
May 17th, 2013 - 14:31
It’s tough to say without being there to diagnose it. Perhaps the check valve is stuck closed or maybe an air pocket trapped in the pump?
Thanks for the inquiry.
May 17th, 2013 - 15:06
Hey Mike
Can you tell me how I can release a possible air pocket trapped in the pump?
May 22nd, 2013 - 08:41
It might be a good idea to get a plumber in there to look at your problems Wayne. It’s tough for me to say for me without checking things out.
May 14th, 2013 - 20:24
I am remodeling a house and neither the sink, laundry, shower or bath are vented. It would be pretty easy to put a cheater vent in the crawl space, but very difficult and expensive to run three new vent pipes through the roof. Here is a rough diagram of what I was thinking…
]
V ]
_____[ ]
[____]
Do you think this would be ok?
Thanks
May 14th, 2013 - 20:26
second try on the diagram.
][
][````V
][````][_____
][____][
May 17th, 2013 - 08:29
Sorry man. Clear as mud to me.
May 17th, 2013 - 08:28
Hi David.
It’s pretty common with older houses to not have proper venting. It’s for these applications where a proper vent is “not practical” to use that the cheater vent exists. So it’s up to your discretion. I have definitely used them before in these types of situations. Good luck!
May 21st, 2013 - 23:37
Have a quick question. I have a park model trailer and in the bathroom there is a washer drain pipe going but it also looks to be the possibly vent for sink/toilet/tub since their is nothing on the roof (trailer originally had ventless toilets, we have since put in low flow toilet). When washer drains toilet gurgles, we plunge the tub to help it and it seems to fix for a few days. It hasn’t ever filled up anything with excess water yet. Does this sound like a venting issue or a sewer line clog issue? We did dump some sewer line solution to clear the line awhile back but the problem came back after a few days.
May 22nd, 2013 - 00:03
And if it is a vent issue (considering it didnt start till after vent away toilet replaced with normal low flow one), where should I install the cheater vent, drain pipe that washer goes into is on left side of sink before p trap.
May 22nd, 2013 - 00:34
Since a pic is worth thousand words… Here is a photo of the setup, far left black pipe is drain tube for washer that hose is in.
https://www.dropbox.com/s/8261vvvv8rajf6r/Photo%20May%2022%2C%2012%2029%2059%20AM.jpg
May 22nd, 2013 - 08:39
Hi Jennifer. In this case it seems that either the drain is a bit plugged or you need to run a proper vent off the toilet… Since a washer dumps a large amount of water into the pipe, the air needs to escape somewhere and a cheater vent can’t do that. That being said, you’re sink could still use a cheater vent to prevent the trap from being syphoned out and smelling.
Mike
May 22nd, 2013 - 09:23
Ok to run a proper vent would this mean through the roof, if so are their any alternatives to a roof run that can be done within the bathroom. I can relocate our washer to the second bathroom which has an outdoor vent, but I wouldn’t think this would resolve the problem of not having a vent in that part of the plumbing, as the other bathroom is not part of that plumbing setup.
May 22nd, 2013 - 16:05
It should be the wet vented 2″ that continues to open air, and yes this can be a challenge at times. You’ll have to decide weather you can deal with a bubbly toilet or go through the trouble of extending your vent. But first make sure that your drains are flowing freely. I hope this helps.