What is venting? 147


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.

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147 thoughts on “What is venting?

  • Yegan Govender

    I have a terrible sewer odour at my place
    Had the plumber flush the line completely to no avail.live in a complex and others are complaining about same could it be the ventilation cos the main toilets just have an elbow at the outlet.please help

    • mike@jaytechplumbing.com Post author

      Sewer smells are very difficult to narrow down. Unfortunately I won’t be able to give you anything worthwhile without seeing it in person. Sorry.

  • Shawn Berry

    A few weeks ago there was a loud bang in the ceiling. Then we saw wet spot on the ceiling in a closet. The vent piping in the attic had a crack in it right where the wet spot was. My question is should the venting run across the attic then up the stack and how does water get in? I fixed the crack i guess is it was 40c below when it cracked. We only have one stack but bathrooms and sinks on both sides of the house.

    • mike@jaytechplumbing.com Post author

      My suggestion would be to move to a warmer climate. -40c is a bit excessive, lol.
      Water will drain through the stack coming through the roof if it’s raining or if snow is melting. Shouldn’t be a lot though.

  • Chris

    I installed toilet with a mascerating unit attached to it and attached the vent to the neighboring sink with 2″ pipe. The unit isn’t functioning properly and I think the venting does not travel high enough above the main sewer drain line. The vent currently sits at about the same height, does it need to be plumbed up through the roof to work properly?

    Thank you in advance,

      • Mike

        Hi Chris. So what I’m understanding is that you connected your vent to a drain. It should for sure be connected somewhere to the venting system. There’s no guarantees though that it will solve your toilet issues, as it could be many different things causing it to malfunction.

  • Marc

    After several flushes,my basement toilet drains slow and there’s a gurgling sound from my bar sink and a sewer smell.I had the toilet sewer line pipe all cleaned and flushed out to the road’so i know its not clogged.Im thinking its a venting problem.Not vented properly.Would a cheater vent work in this situation?where should it be placed?
    Any info would be appreciated

    • Mike

      It’s hard to say without seeing the situation but it could very well be a venting issue. A cheater vent under your sink would probably be the best location.
      Thanks for the question Marc.

  • Jerry

    I installed a dishwasher in the main floor kitchen a while ago. I have not experienced any problems but after reading about venting I wonder if my installation is correct. The flexible pipe that came with the dishwasher was looped up to just beneath the counter (behind the dishwasher), then run through the floor to the basement. There it goes from a 3/4″ to 2″ adapter, then about 6″ vertical fall, 90 degree bend, another 12″, into a p-trap. I used ABS pipe, by the way.
    Here’s where I’m not sure if I did the right thing. I had to get the drain across the room into 2″ pipe diagonally across from where the drain enters the basement. So I ran 2″ pipe about 6 ft, straight across, into a 90 degree bend, then another 5 ft into one of two 2″ pipes side by side vertically beside the laundry tub. The fall was just a little more than 1/4″ per foot. The pipe I connected to with a proper tee has a cleanout on it, but I don’t see any connections on it. It goes into the concrete floor. Would this be a vent pipe? Again, I’ve had no issues, but was this done correctly?

  • Rick perez

    I had back up issues in both bathrooms. I rented a 100 foot snake and ran it to the sewer all 100 feet and then back under the house. The back bedroom bathroom is now working but the toilet and shower in the hall bathroom are still clogged.Will venting solve this problem,finally

    • Mike

      It’s unlikey that an occasional loud noise from the roof is from the vent pipe being clogged, I would be more inclined to think it’s an animal.

  • AC

    Just found out there is no venting on the home I am in. Have not been well for a few years and now wander if I am sick from this house. Will it help right now if I keep the windows open a bit until I find out what to do. Also, a plumber said that a roof vent isn’t needed as it would be costly and he would use cheater vents. I don’t think that is good enough. Couldn’t a vent be run on the outside to the roof instead of tearing a wall apart.

    • Mike

      Hi AC,
      The purpose of venting to to protect the trap which in turn protects smell from entering the house. A cheater vent also accomplishes this. Obviously a stack through the roof is the most ideal situation but you’ll need to get a local plumber to figure out how to best do that if that is the route you choose to take.
      All the best with your health however, whatever the cause of that is.

  • Matt

    Will a 2 inch vent that comes out of my lift station work for a toilet and shower that are 25 feet from lift station that is in basement, it is 4 inch from toilet to lift station? Thanks

  • Delbert

    Why would my toilet not hardly flush at all, the water just swirls around and does not flush all the way and the tub next to it drains very slowly but it does all drain in time? I have checked the clean out under both systems from the basement to include removing the trap on the tub and snaked the drains in all directions. The vent going through the roof and down seems clear of obstructions. It is a 3″ PVC pipe and I can smell sewer through it. Please help. Thanks

  • Randy Valentino

    I had a plumber over and didn’t vent the toilet because of the difficulty going thru attic,therefore I need a way to vent as to what I’m reading here you should vent your toilet.It was vented originally but plumber said not necessary.Are You able to put the vent @ the end of the 90 just before the toilet.

  • Sheldon Carter

    This article described my problem exactly. There is one in there but it is not working properly.
    Thanks for the helpful information.

  • deb fine

    In 2013 we had a new flat roof installed on a 3 story condo. The stacks have all 3 units flow into it. There are three stacks: one for the bathroom, one for the kitchen and one for the wet bar between the livingroom and kitchen.

    Since the new roof was put on, when the upstairs owners flush their toilets (2 separate condos), use their bath sinks and tubs and do their laundry (in bathroom) i get a sweet smell in the bathroom which goes through the house which eventually turns to a stale smell (like house has been closed up for a while). I can also smell the sweet smell outside where the sewer pipe comes up through the ground for access.
    I noticed in the early morning hours one night, sitting on the toilet, there was a flow of air coming straight from the door to the toilet base. I do not recall having any windows open as it is cold outside.

    Do you have any ideas why the smell is occurring or suggestions in pinpointing the problem?

    I had my bathroom redone in 2009 but no problem until the new roof in 2013.

    I have a call into my plumber to ask is it possible my toilet seal is broken or something wrong with it.

    Thanks for your reply.


    • mike@jaytechplumbing.com Post author

      Hey Deb. Smells can be hard to track down. In my experience its usually one of three things… Bad venting (maybe stack was plugged temporarily during roofing and forgot to remove cap), drainage backing up, or floor drain trap is dried up and needs to be filled with water. Check these things and see if you can solve it.
      Good luck.

  • mark jones

    the vent for the upstairs bathtub has water coming down the outside of the pipe.I have checked in the attic and there are no leaks from the roof.This only seems to happen when the temperature starts to drop.

    • mike@jaytechplumbing.com Post author

      You’ll just have to track down where the water is running from. Look for water stains, or maybe probable condensation areas, or a bad flashing.

  • Ann

    We are having our bathrooms renovated and I noticed that when they put up the vanity they used screws that went into a pipe. They said it is an air vent pipe and it was fine but I’m not sure I trust them. What can I do?

    • mike@jaytechplumbing.com Post author

      You should always fix a pipe with a hole in it. Cut the pipe where the screw was and put a coupling there instead.

  • S. Ali

    It is quite helpful information. Though, I little late for few things that I have already done without knowing that it was okay to have the wet vent but practically it was not draining the sink. Now I have ran a separate drain for the sink and venting it to the “wet vent”. My question is, I am dropping the drain into a vertical 3″ sewer venting a 1.5″ y off the 3″ and another vent off the 1.5″ and combining two other vents out into the main vent out of the house through roof. In terms of gas flow, water drain and clogging I see it much better, actually perfect, but will there be any code issue ? Before it was done in a way that the sewer drain was hanging 8″ out of the basement ceiling and the wet drain had no slope for the sink. I can share some pics if there is a way. What would you say?

  • Jim Manolas

    Question. would a higher/longer vent stack have more stink -evacuating ,air exhausting “pull’than a short one and if so why ? Thanks,Jim.

    • mike@jaytechplumbing.com Post author

      Hey Jim. The idea of venting is to protect the traps from syphoning and goes out the roof to have a safe place to “breathe”. Pulling or higher/longer is not really so much a concern. Thanks for the question.

  • nate

    Hello i am having an issue in my basement. I recently repaced my old toilet with a high efficiency toilet. But now when the seage tank pump turns on the toilet bowl empties.I didnt have this issue with the old toilet. The tank does have a vent but it is tied in between the sink and the toilet. So i am pretty sure the rush of air is sucking the water out of the toilet. Is it possible to instal a cheater vent right off of the sewage tank.

    • mike@jaytechplumbing.com Post author

      That might help as long as there is still a vent somewhere. I’m thinking the vent is probably undersized.

  • Heather

    I have a kitchen sink with the drain pipe going back into the wall – vent goes up, drain goes down into drain line. The pipe in the wall is leaking – rather than tearing out the cabinets and drywall to repair the pipe buried in the wall can I re-route the drain straight down into the drain line as long as I use the old drain as part of the vent under the sink – ensuring it slopes up

  • john

    having problems with our toilet and washing machine we have a septic tank and a grey water tank however I noticed today no plumbing vent threw roof, live in a cottage with crawl space . Toilet barley flushes and washer backs up sometimes leaving water all over floor does it need a vent

    • mike@jaytechplumbing.com Post author

      Yes you need a vent but it also seems like the drain in your cottage is a bit plugged. You may want to run a sewer snake through there.

  • Iris

    Hi Mike,
    My question is similar to Lawrence’s. I have a SaniFlo pump which will allow my tub, sink and toilet to exit through the sewer drain that is two feet above the floor. The pump is connected to the house venting. Can the sink have a cheater vent? It drains into the pump. Thanks.

  • Lawrence Pilcher

    Hello Mike,
    I’ve run through the posts and didn’t see one like what I intend to do.

    I have a basement room to remodel. It currently is our laundry room and 13′ x 8′. In this room I have the waste out line for the home with a 2″ dry vent not far from the exit through the foundation wall. The waste line is about 6″ OC off the floor.

    Using a sewage basin in one corner of the room, I want to add toilet, a stand up corner shower, a sink and of course the drain for the washing machine.

    I haven’t laid out the plans for each fixture yet, but can I do all this with just one vent? Or should I plan on using a cheater on something? Maybe cheat the shower and washing machine?

    Thanks for your time,


    • mike@jaytechplumbing.com Post author

      You can connect all the vents together for sure, but you may not use a cheater vent on a sewage pit. It simply will not work… air must go in and out of the tank, but a cheater vent only allows air to flow in one direction. I hope this helps.

  • Bashir

    My second story bathroom sink started to clog up. I have tried some drain cleaners, including commercial strength to no avail. A plumber snaked the drain (25ft) and it still drains very slowly. The water drains about the first minute before it starts backing up into the sink. Which tells me the blockage may be a ways down. However the plumber felt it was due to a lack of vents. The house is 20 years old and in the 8 years we have leaved here, we have not experienced problems before. I am baffled why after 20 years, a drain without a vent, if that is what\’s causing this would now give us problems. Does this make sense?

    • mike@jaytechplumbing.com Post author

      It seems to me that it must still be a bit plugged somewhere. Drain backups can be quite a challenge sometimes… maybe approach the snaking from a different angle or see if you can cut in a clean out further down the line. Hopefully you can get it flowing properly.

  • Valli

    Sorry, but I have another question. I guess you can tell, this plumbing thing is driving me slightly nutty. And all the plumbers in my area of Maine are too busy these days to answer some of these questions or their answers are not helping. Or they’re just too darn expensive. So…. I’m looking for a good Tankless Water heater that uses Propane. Everyone tells me to get Rinnai, but they are SO expensive, I’m sure there must be another brand suited for my situation that’s less expensive. Plus, if Rinnai doesn’t install it with their own plumbers, I hear the warranty will be invalid. My cabin is very small, uses only Solar for power with generator backup, so it has a soft-start pump in the new well. It has one bathroom with sink and tub, and a kitchen sink. NO other appliances needing water. Is there something that could work for me in this situation? The water in the northeast is very cold (so it takes longer to heat) and this cabin is seasonal, closed down for the late Fall, Winter and early Spring. I have a propane tank on the property so it has to use this as it’s fuel. Not electric. Thanks!

    • mike@jaytechplumbing.com Post author

      In my experience Rinnai has been a great product and one that we do recommend. If you’re going tankless it will be expensive. I think you have to decide whether to want to save money (traditional propane heater) or save energy (tankless).

      • Valli

        Two questions (sorry) but are there other Tankless water heaters that are as good as Rainni but maybe less expensive? AND…..can you explain what a “Cheater Vent” is? Thanks.

          • Valli

            I just talked to a building contractor, asking him about venting. I was surprised at what he told me. If it is true than it throws off everything I thought I understood about venting. He said that EACH plumbing fixture has to be vented through a common pipe/vent. But it was my understanding that there only needs to be one vent in the roof for the whole house. And that vent does not need to be attached to the pipes/plumbing to work. What am I missing? thanks!

          • mike@jaytechplumbing.com Post author

            Every fixture needs to be vented and the vents connected together and running up to protrude through the roof.
            Thanks for the question.

          • Valli

            Thanks for your answer. So, let me ask you this. The small cabin that I bought only has pipes on fixtures that lead out to the septic. So far there are no pipes to bring in water from the very new well. So, it has a kitchen sink, bathroom sink and tub and toilet. Each of these seem to be draining as they are supposed to. So, when I do put in fixtures to bring in water from the well, why would I need venting if so far all seems to be working fine? Or will the new fixtures need vents even though the existing fixtures don’t seem to need them, as far as I can tell. Thanks again!!

          • mike@jaytechplumbing.com Post author

            If a fixture isn’t vented then you risk siphoning out the trap… without water in the trap then you will get a sewer smell in your house/cottage. It will still drain fine but the purpose of venting is to protect the trap seal.

  • Valli

    Thanks for the venting information. I just bought a small off the grid cabin in Maine and though it has a septic and plumbing for waste water and toilet, it does not have plumbing for bringing in water from the newly dug well. I plan to do that in the Spring. But the plumbers who have come to give me an estimate on the cost, all told me there is no vent on the roof and some worry about that, others do not. One said that as long as the toilet seems to be flushing ok, then I may not need a vent. BUt, I worry that down the line or after they put in the rest of the plumbing, it could make a big difference. I’d rather NOT pay for a vent in the roof, since I think it could cost a lot. What do you think I could use instead of a vent in the roof? Or is it absolutely needed? Thanks!!

    • mike@jaytechplumbing.com Post author

      The idea of venting is to protect the traps from siphoning out and therefore causing a smell in the cottage. Although it is code to have a vent through the roof, an easy solution would be to put on an air admittance valve where needed. This will break a siphon. On the flip side, it will limit you in the future on things where you do need a proper vent such as a sewage tank and pump. (Maybe for basement washroom). I hope this helps.

  • Greg

    Hi, I was planning on installing a toilet in my basement. I was going to join into the main drain which runs across and underneath my concrete floor by using a \”Y\” My question is about venting. The main drain runs across my basement and then straight up a main perimeter wall where everything else connects into it. That stack is 3\” diameter pipe and also next to that coming out of the floor is a 1-1/2\” pipe. I assume this is the vent? My new toilet will be approx. 5 ft from the \”Y\” I will add and and overall, approx 10 to 15ft from the main vertical stack. Will i need additional venting for my new toilet? Thanks in advance.

    • mike@jaytechplumbing.com Post author

      Yes you will need to vent your toilet. The 1-1/2″ vent is likely serving as a vent for something like a floor drain, but all fixtures need a vent. Thanks for your question.

  • Bobbie

    we replaced the cheaper ones with better ones. thanks!
    turned out it was a dead rat under the bathroom floor. we had poisoned and one was under there. yikes! what an awful smell! we had to wait it out as it would have been so costly to tear up the floor and search for it. I want to let folks know that activated charcoal really does help with odors! cut the smell atleast in half!

  • Melissa

    We have a basement bathroom. The shower is rarely used. One reason is because the drain backs up. It especially backs up when we use the washing machine. Black chunks and other debris come up through the drain. It smells horrible! We keep a towel shoved into the drain to keep the backup from happening. Recently the sink started backing up. We have had plumbers out to look at it. They each snake the drain and tell us to not use the garbage disposal in the kitchen too much. We don\’t use the disposal except to throw any leftover cereal in the bowl down. Could there be another issue?

    • mike@jaytechplumbing.com Post author

      Hey Melissa. There is definitely something plugging up your drain still. Either the plumbers didn’t remove the plug 100% or there is something in the drain causing the blockages such as a broken pipe, rough edge, or back slope. I would try snaking it out better as the first course of action.

  • jurij

    Hi I was about to re roof my house and whoever built this house put 3 vent pipes out the front side of the house all within 5 feet of each other. I was wondering if I were to take and tie them all 3 together and then run them to the back of the house which would be about 15 feet for the lowest one would this be wrong to do? I would like to make only one hole in my roof not three. Thanks Jurij

    • mike@jaytechplumbing.com Post author

      Vents out the front bother me quite a bit too and especially multiple penetrations. I would definitely do what you are suggesting. Good thinking Jurij.

  • Rob Lane

    Hi How many 1 1/2 vents from various fixtures can you connect to a 3″ stack vent in attic area? Is there a maximum number? Great comments.

    • mike@jaytechplumbing.com Post author

      There are some calculations you could do for that, but the truth is that if you’re in a residential building you’ll virtually never load up a 3″ vent with too much load. Put in as many 1 1/2″ vents into it as you like.

  • Bobbie

    can cheater vents fail? we are having an odor in one bathroom. last time the plumber replaced the black AAV under the kitchen sink with a Studor design after snaking the k. sink with no results. odor gone. I checked the other black ones in the bathroom, and the filter? is very dark—- can they get plugged up over time like an air vent getting dusty/dirty? and need to be replaced? would you then get an odor? if so I can buy the white studor ones- are they better? if the filter is dusty/dirty- can you get an odor? The vent was only $15- much cheaper than a plumber call. (I have 2 sinks in the master bath- both have the black vents. we are also on septic system.)

    • mike@jaytechplumbing.com Post author

      Hey Bobbie. Yes a cheater vent can fail over time and may need to be replaced. The better ones that we use are from Oatley. Thank you for inquiring.

  • Bill

    Hi. I have been working on the plumbing system of a 2-storey residential. However, I’m having troubles with the ventilation system because the bathrooms were located far from one another. I wanted to have one vent stack thru roof only, but the solution I got is otherwise. Like having 3 vstr to have it well ventilated. I’m not familiar with the ventilation system that’s why I’m asking.

    ground floor:
    1 bathroom with bath tub in the master’s bedroom(left side)
    1 bathroom near the stairs(left side)

    along side the master’s bathroom there’s an enclosed dirty kitchen with floor drain and kitchen sink.
    infront of the dirty kitchen is the main kitchen with 2 kitchen sinks.

    second floor:
    1 bathroom (left side)
    2 bathrooms side to side (right side)

    roof deck:
    1 kitchen sink
    1 bathroom
    1 outside jacuzzi

    this is for anyone who might want to answer my question

      • Dan Jouett

        we have a brand new house 1 year old. were finishing the basement and bathroom down there!! it is rough plumbed for a 3/4 bath. we went to install shower pan today and got everything hooked up. poured some water down the drain and nothing happened the water just sat there. and still is even after a few hours. 2 in drain line. the toilet line is working and so is the sink drain. just not to sure what is going on with this shower drain please help thank you


        • mike@jaytechplumbing.com Post author

          I have had it a couple times that during construction something gets put down the drain such as tile grout or drywall mud and hardens in the trap. Maybe take a flash light and look down to see if that’s the case.

  • Frank

    I have an unfinished basement and would like to install a 3 piece washroom. Can I tie into existing stacks to vent each fixture? Conversely, when can I not tie into a stack to vent the fixture?

    • mike@jaytechplumbing.com Post author

      You can use it as a vent as long as there is nothing draining into it as well and it must tie in above the flood level rim of the highest fixture.

  • Chris

    Hi Mike,

    I am looking to rebuild a small 3 piece bathroom in my basement and have a question regarding proper venting as there is currently no venting (house was built in 1952). I’m looking to wet vent 2 of the 3 fixtures using an AAV (cheater valve). If I run a 3” pipe from the toilet to the main soil pipe and have 2 separate branches off of the 3” pipe for the shower and sink, each using 2” pipe, can I install an AAV at the sink to successfully wet vent the shower and toilet? Refer to the diagram below for clarification. Note that the distance between the shower and sink drain is 6’ and the distance between the toilet and sink drain is 4’. House is located in Ontario.

    Thanks in advance!

    [TOILET] ——————————————————————- (TO MAIN SOIL PIPE —>)

    • mike@jaytechplumbing.com Post author

      Hi Chris.
      You have it pretty close to correct and you could actually eliminate the shower vent if you do it correctly also. Try and plumb it in like picture #2 on this page, only don’t vent your shower (tub in the picture) if the drain is shorter than 5ft to the y connection.
      Good luck!

      • ray

        Hi. I noticed you connect the venting of water closet to a smaller pipe in your 1st picture on your website. Is it an appropriate design? Will it affect the atmospheric pressure inside?

        • mike@jaytechplumbing.com Post author

          I think it’s just a poorly drawn picture. The flange, pipes and fittings should all be 3″ (except for the wet vent of course).

  • Dennis

    Every month or so my sewage does not drain out of my house. I remove the clean out cap and it releases the pressure, then the waste flows out like a river. Is this a vent issue? I checked them to make sure they were not blocked. I am not sure what to do. I have lived here for 15 yrs and never had an issue. Any suggestions?

    • mike@jaytechplumbing.com Post author

      That definitely sounds like a venting problem to me Dennis. It’s going to be very difficult to know where the vent is plugged if that’s the case but there should be a stack that continues all the way up and through the roof. One option (although a bit difficult to execute) would be to run a snake from the roof down the stack and try to create a clear path right through the system.
      Let me know if that helps and what the result is.

  • Shawn

    Hi Mike
    Nice to talk to an expert

    I am building a new house just east of Cobourg On and I am doing the rough in pluming by myself .. Moneys tight .. Venting is the hard problem .. I have a double vanity in the main floor bath along with a washing machine ,, I also have a 1-1/2 vent coming from the basement toilet right up in the wall between the vanity and the washer .. My question is ,, I am running 1-1/2 abs vent horizontally (Slight angle 1/4 per foot ) from the double vanity across to the 1-1/2 vent from the basement toilet and then to the washing machine and then to the 3 inch stack .. Can I tie all 3 together using 1-1/2 abs ..


  • JJ

    We are in a contract to sell an 50 year old home we have lived in for 11 years. The buyer inspection is this Friday. In getting the home ready for inspection I have realized that there is no plumbing venting. We have 3 sinks, 2 bath/showers, and 2 toilets. Is the inspector going to kill the sale price of our home because of the lack of venting?

    • mike@jaytechplumbing.com Post author

      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.

      • Jennifer

        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.

        • mike@jaytechplumbing.com Post author

          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.

  • Jennifer

    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.

    • Jennifer

      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.

  • David

    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?

    • mike@jaytechplumbing.com Post author

      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!

  • Wayne

    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?

    • mike@jaytechplumbing.com Post author

      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?

      • Wayne

        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.

          • mike@jaytechplumbing.com Post author

            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.

          • Wayne

            Hey Mike
            Can you tell me how I can release a possible air pocket trapped in the pump?

          • mike@jaytechplumbing.com Post author

            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.

  • Kate

    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.

    • mike@jaytechplumbing.com Post author

      Thanks Kate. I actually know a great company in Alberta… Blackstone Mechanical. All the best with your career!

  • Drew

    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?



    • mike@jaytechplumbing.com Post author

      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.

  • Stan

    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

    • mike@jaytechplumbing.com Post author

      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.

  • josephVelder

    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.

  • josephVelder

    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?

  • Arthur

    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..

    • mike@jaytechplumbing.com Post author

      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…

  • Joseph Finch

    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.

    • mike@jaytechplumbing.com Post author

      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.

  • Lynne Dover

    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

    • mike@jaytechplumbing.com Post author

      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.

  • david


    • mike@jaytechplumbing.com Post author

      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.

  • Tammy

    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.

    • mike@jaytechplumbing.com Post author

      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.

  • Gayle

    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.

    • mike@jaytechplumbing.com Post author

      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.

    • mike@jaytechplumbing.com Post author

      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?

  • stewart

    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!

    • mike@jaytechplumbing.com Post author

      In my experience that falls under the duties of the hvac contractor. The v in hvac stands for ventilation.
      I hope this helps.

    • mike@jaytechplumbing.com Post author

      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.

  • plumbing

    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.

  • unknown

    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

    • mike@jaytechplumbing.com Post author

      I used a template and redid it to look the way that I wanted. Thank you for the comments.