Your plumbing system should not pass gas indoors!

Lets get something clear right off the bat.  This is about your houses plumbing—not your personal plumbing.

When I first started doing plumbing in 1971–at least for money–venting island kitchen sinks was a bit of a problem.  Every plumbing fixture needs a means of venting the drain line so that water doesn’t get sucked out of the trap of the fixture—-which could allow sewer gases to enter the home.  Somehow sewer gases and the smell of fresh baked bread or homemade pizza just don’t go together.

We had to create all kinds of strange assemblies of pipes to create this venting–it worked, but was time consuming to construct and took a lot of additional pipe.  Pipe and time equal money.

Along came the “auto-vent” or “air-vent” (sometimes called a “cheater” vent).  This mechanical device had a spring loaded gasket inside that would allow air to flow into the pipe but not let sewer gases out–or, in the event of the pipes flooding, the device would not allow sewage out either.

When you think about it, keeping sewage out of the home is a better idea than keeping gases out!

These vents could be installed right at the fixture location—-saving tons of time, pipe and money.  Unfortunately most jurisdictions did not allow them–except in the mobile home industry–where they are still allowed–go figure.  Here is a picture of one of these vents that I found installed at a kitchen sink in new construction that had to be replaced after I found it.

Air vent

Air Vent or Auto-Vent

If you can see a spring inside the cap, it is an Auto-Vent.

Spring visible inside an Auto-vent

Spring visible inside an Auto-vent

At some point in the 90’s, a new type of air-vent could be found in the neighborhood–called the Air Admittance Valve–or AAV.  AAV’s quickly gained acceptance in most jurisdictions and are now widely used.  These valves are different from Auto-Vents in that there are no spring mechanisms that can fail and they have screens to keep out critters.  They have a simple EPDM diaphragm (trust me–want the initials stand for is not all that important—synthetic rubber for short) that allows air into the drain under negative pressure and seals tight under positive pressure.

AAV’s, to meet approval for use in residential construction, have to demonstrate that they can go through 500,000 cycles without ever passing gas—-roughly equivalent to 30 years–man I sure wish my plumbing system could do that!  Here is a picture of a modern AAV on a laundry sink drain.

Air Admittance Valve

Modern Air Admittance Valve

While a really simple device, they must be installed within 10 degrees of vertical, they must be installed on the welded-pipe side of the trap, they have to remain accessible and they cannot be the only means of venting the plumbing system.

Air Admittance Valve

Air Admittance Valve (AAV)

These Air Admittance valves come packaged with a rubber band that needs to be removed at the time of installation–I sometimes find them with the rubber band still in place–rendering them non-functional of course.

AAV with the protective rubber band still in place

AAV with the protective rubber band still in place

So, never–ever–pass gas again!

Now what fun would that be?Gas puts a smile on your face!


By Charles Buell, Real Estate Inspections in Seattle

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  1. I install a new toilet. When the toilet flushes it sucks the water out of the trap of the bathtub. Can cheater vents be used on a bathtub to solve this problem?

    • You might have a partially or totally clogged vent stack. Check this first.
      Or you may have a non vented water closet or a water closet with a reduced vent that is too small for the flush. This last item is very rare though.

  2. Mr. Buell:

    Can I install a Studor Mini-Vent or similar vent on a laundry-tray pump setup with the drain line 7′ above the pump? The new rig is a Zoeller Model 105 laundry tray pump that uses an M53 sump pump — a very durable pump as I’m sure you know — inside a plastic box that has a 2″ vent port. It is replacing a 25+ year-old Westinghouse model that used only a 1/2″ hose port for a vent, from which I ran a piece of garden hose up the side of the laundry tub and into the tub. That worked fine but of course did not shut off the air flow to or from the pump box below the tub.
    I never had a problem with sewer gas smell, possibly because the Westinghouse float switch was set to leave a few inches of water in the box, and the discharge was at the bottom of the box, so I assume that little bit of water functioned like a trap to provide a seal. Also, I of courese had a check valve on the discharge line. I’d love to get the same Westinghouse or similar model, but I can’t find anything like it.
    The non-vented laundry tray pump by Bur-Cam uses an electronic switch, but I prefer a float switch, which nearly all vented models use. Also, I know Zoeller makes good pumps, but not sure on Bur-Cam.
    So — can I use the Studor Mini-Vent? Venting outside is not an option.
    Thanks much and your site is a fine one.

    • Charles Buell says

      Send me some pictures of the installation privately and I will see if I have an opinion for you 🙂

    • My liberty 404 tray bucket pump can not use these vents. My pump blows air out so it has to vent outside. I tried stooter vrnt, but it airlocks my pump up, because it does not let air out the minute I take off scooter vent it works fine.

  3. Katie Peck says

    Hi there! We have been struggling with some plumbing problems for a few months now, even with licensed “Master” plumbers doing work. We can’t seem to get straight answers from anyone.

    Here is a summary of our situation.

    Our house has one main drainage line from the kitchen that runs perpendicular to the sewage main exit from the house, in the basement the sewer main is about 5 ft above the floor. The line from the kitchen was moved to allow for remodeling but has been properly graded. About 40′ from the kitchen sink there is a laundry sink and lift pump to pump the laundry water up and into the sewer main. We have a studor vent under the kitchen sink and a studor vent for the lift pump. This work was just completed and what is now happening is a back up of air pressure in the laundry pump. It results in a slow drain so the water is backing up in the sink, threatening to overflow if we aren’t there to watch and release the pressure in the pump by removing the cap on the pump.

    We called the plumber who is on his way over now. He says maybe the guy who installed the pump didn’t read the directions and the thing can’t work with a studor vent and may need to be vented outside.

    I’m not paying for any more plumbing work from anyone until I know for sure what is going on here. We used the pump with NO issues before with no studor vent, just an open pipe. Can we not just return to this set up?

    Any suggestions or expeirence with studor vents and laundry lift pumps????? HELP!

  4. Marti McNamara says

    I live above a restaurant. Sewer gas has been an issue for three months. There are two AAV’s in my condo, one under the sink and the other under a wash tub in the laundry room.
    The restaurant sewer line and my line has to have a connection somewhere along the line. Is it safe to cover the the two AAV’s? This is the third AAV replacement in my laundry room. I cannot live like this. Help!

    • Charles Buell says

      If you are having a problem with AAV’s you need to call a plumber pronto—and it sounds like not the one you have used in the past. I have never heard of an AAV failing so I am thinking there must be something else going on. Are you sure they are AAV’s and not Auto-vents? It is certainly not ok to cover any vent.

      • Marti McNamara says

        The last plumber called them auto-vents but it is the same as the one you have displayed at the top of this column. I have had three plumbers replace these vents in the past three years. Are these vents suppose to be connected to a roof vent?

  5. Marti McNamara says

    I have a picture of the installed AAV. How can I send it to you?

  6. Toni Buchanan says

    I have an old cottage that we now have a grinder on all the plumbing except the kitchen sink which just goes to a old discharge in the yard. We have been having issues with our sink backing up. So we rented a drain snake and we had no resistance or even nasty stuff come out it was actually pretty clean. So we change the piping under the sink and go to the well box to be on a slant for better drainage and we put one of those air valves like you were showing and raised the pipe that it is on up to about six inches under the ceiling in the room its in. My question is are the gases going into that room out of that vent dangerous to breathe and our drain still backs up just not as fast. If we go all the way out the roof do you think that would solve our drain problem. We are renters and my landlord has been trying to avoid is going through the roof. What do you think.

    • Charles Buell says

      From everything you say the only thing that is very clear is that you need a licensed plumber to figure this out. I suspect there are other more serious issues going on. Don’t mess with this problem yourself please.

    • You may have ran a snake through the line but if it is food/grease/soap build up in the pipe the snake can pass through it with little effort and when you remove the snake the build up simply falls back and continues to clog the passage.
      If you snake came out with black nasty smelling grease looking coating, this is what may be wrong.
      A power washer like the Clog Hog takes care of this in most cases where it is only grease/food/soap build up.

  7. Toni Buchanan says

    Thank you but at this time that does not seem to be an option because that would be up to my landlord and she keeps putting that off. That’s why I was wondering if the gases were coming back into my house.

  8. Patrick Stefan says

    This is really helpful! I installed an oatey AAV for a kitchen sink that did not have its own venting from when the previous owner did a remodel. Everything seemed great, but every once and a while I get a hint of sewage smell that lingers for about 30 min. Is the AAV bad?

  9. We have an AAV under our sink where a disposal is also present. We get sewer gas smell from time to time – is there a way to check this valve or is the method to throw it away and replace?

    • Charles Buell says

      Pat there are so many other sources it could be. I would be hesitant to blame the AAV unless it is actually an Auto-vent. You should have a plumber look at your setup if you are indeed smelling sewer gases.

    • the disposal could have clogged up a large portion of the trap and drain line and reduced the required wet trap depth.
      If this is true then it is easier for back gasses (gasses from the sewer system you are on) to force back fumes through a dry or dryer trap.
      This even happens on Septic systems.

  10. I have a sewage pit in my basement to service a bathroom and a small hair salon. The vent stack is 1 1/2″ leading to the basement. The sewage pump is a 3/4 HP with 2″ discharge. My concern is that my vent stack won’t handle the vacuum of the pump without siphoning from my traps. Is the aav a good option as a complete vent or should I still tie to the stack?

    • Charles Buell says

      Sorry, Carl, but I cannot adequately answer your question due to all the variables. Consult with a licensed plumber.

    • actually it depends on the rating of scfm your pump will draw. your pump mfg can tell you what that is.
      secondly the distance that the vent stack has to draw may be a factor.

      try to run the pump without the stack at full length. you can do this by cutting it at eyeball height and letting the pump work while you are watching to see if it makes any difference. if it does then you may have too small of a vent, too long of a vent, a combination of both or a clogged vent somewhere.

      You can reassemble the cut pipe with a no hub clamp or ct adaptor with stainless steel straps.

  11. Ray and Judi Jelinek says

    After 23 yrs we replaced our tub with a shower and changed the vanity. We now have a sewer gas odor coming up through the sink. We can’t afford to spend any more money on this bathroom and are hoping it is a problem we could solve.

    • the only way you can have sewer gas coming up from the sink or sinks is if the trap is dry or does not have a minimum of 2 inches of water in it at all times. I even believe 3 inches is better.
      you can change this easily with some pvc ptrap parts that you can buy from any hardware store. you are simply lowering the actual ptrap or ‘u’ looking lowest part of the drain under your sink.
      if this works you know the answer.
      if it does not then you need a master plumber to come out or maybe even the local city inspector could help.

  12. We had to have 50 feet of galvanized sewer pipe removed from our very old home and had new plastic put in along with pex water lines and a new venting system put into our upstairs bathroom. We put in a new toilet, new sink and new tub. After paying a substantial amount of money we find that the venting system is not working. When draining the tub or sink the toilet will gurgle and spit water. This does not happen all the time but usually every morning at the least. The plumbers have been back several times and last time they extended the venting system up to the attic with AAV. This did not work so the AAV was taken off only until they come back in next day or two so they can extend it even further up through the roof. We have been dealing with this mess for exactly 5 weeks, What are the chances that this will work? Cost is another 375.00 on top of the $4,000.00 we paid previously, Any suggestions?

    • sorry was not galvanized it was cast iron

    • Charles Buell says

      Sounds like one or more of the vent caps is still capped off from testing perhaps. The plumber should be able to easily sort this out for you. But it sounds like you might need a different plumber 🙂

      • I agree. somewhere there is a vent line not open or is clogged by squirrels or nests or ???
        Sometimes you can even get one clogged when contractors wash/rinse debris down a sewer opening such as a water closet.
        a video camera would be my first choice to run in every line that was replaced or is new.

  13. Hi Charles,
    I’m replacing my 6″ deep kitchen sink with a 10″ deep sink that needs all the space it can get in my 36″x24″ sink cabinet. I have the AAV vent you described and I noticed it is on the way. Is the vent absolutely necessary? Is it really a must have? Can I just cut off the pvc the vent is attached and put some sort of mesh on the pvc (to prevent critters as you put in your post)?
    The sink MUST be installed (for reasons I cannot get into here). Now it’s just a matter of what should move and what should be removed.

    • Charles Buell says

      If you have an Auto-vent now, you will need a vent when you change the sink. It should be the AAV type though and you should be able to figure out a way to make it perhaps not as high as it was before. Without seeing your configuration I can’t say for sure though. Your plumber will be able to answer that.

  14. Bob Goldsmith says

    Great article! Now I have a question for you. Along these same lines at my last 2 homes we had septic odor coming out of the roof stacks. Can these vents solve this type of problem installed on the roof vents? Odors were particularly noticeable after someone used the shower, etc. Also warm weather seemed to make the odor worse.

    • Charles Buell says

      This is very common with homes that have septic systems and typically it might be my first indication that the home has a septic system if the listing doesn’t already state it. I hear there are charcoal filters made for these vents above the roof to deal with these odors but I really don’t know much about them—or even whether they are code approved.

      • Bob Goldsmith says

        Yes, did I not mention we had septic? It was pumped anew for the sale so I’d think that was not the issue, rather is the direction the odor is traveling indicate a structural (bldg. or otherwise) anomaly that is making this odor noticeable? Where is the gas generated in the tank supposed to go and via what path?

    • if your septic system is not vented at the actual septic tank it can belch back into the house these fumes.
      there is a 4 or 6 inch line connected to your septic system.
      if you locate it and if the contractor did the right thing there should be a clean out just before the septic system.
      If there is, you can extend this opening up to say 8 feet and see if your roof vents don’t calm down.
      If there is no clean out, you need one, and a plumber, or you might be able to do this if you know exactly what you are doing and install a two way clean out fitting and extend it up with 8 feet of pipe.
      Never install a vertical pipe like this without some support.
      Drive a Tpost next to it and clamp the pipe to the tpost for the trial period.
      You may even find out just leaving it this way will result in a permanent fix.

      your distribution lines and your tanks are also suspect.
      Have your tanks pumped out and your distribution lines inspected if this fails.
      A clogged chamber can cause this belching to happen especially with no vent at the septic tank.

  15. Dealing with an icky smell in old farm house. It is not the septic system, just had it pumped. Farmer plumbing for washing machine, no p trap, but pipe goes up over a joist then back down. The toilet is tight. Just replace an old can trap with p trap under tub. The washing machine joins into tub drain. Just had plumber put AV under tub and under vanity in bathroom. Still seem to have some odor. Septic man with ‘smell tester’ said the smell is blackwater smell, not sewer. So what is the next step. This house is in a location that does not really have to meet any codes.

    • Charles Buell says

      Carol, sorry, I have no advice for you. If the plumber was not help, I recommend asking a different plumber.

  16. After decades of plumbing in Phoenix, I am in rural west Texas, sort of retired. I am still appalled that folks think pumping a septic tank will eliminate malodorous gases. If that were the case, we could just use an open bucket and empty it when it started to age. If one is getting a sewer odor in one’s yard, maybe a vent is not high enough or there is some terrain issue is causing a downdraft that is carrying ofors downward or maybe the leach field has become saturated or a vent is actually broken — low enough to carry those fumes into the path of outdoor living. We just did a bunkhouse and it was the first time I had seen the AAV used outside of those kitchen islands dilemmas of the 80s. Fascinating invention, great for maintaining trap function, but there still must must must be at least one conventional vent for that sewer gas. Keep up the good work. Eva

  17. Just moved to FL and looking to replace some vanities. They all have AAV. Is there anything different to change them out here as compared to stack venting in the Northeast?

  18. We have pro-flo AAV’s under all of the sinks in our 1 year old home. 3 out of 5 sinks in the house frequently have horrible sewer smells under them. From what I have read these are not supposed to go bad for 30 years. Do you think the valves need to be replaced?

    • Charles Buell says

      Pro-flow makes both auto vents and air admittance valves—can you post a picture of the one you have. Do you know there is at least one open vent to atmosphere?

  19. I have a bathtub with a vent that goes up vertically and then crosses ove 6 feet to meet the main vent. I have snaked the main vent and there is no blockage, and when running a hose down the line, water reaches the bathtub vent, but suddenly there has been an issue with the tub not draining unless you start it with a plunger. I have snaked all the drains with an auger and there are no blockages all the way to the main sewer line out of the house. All sinks and dishwasher and laundry are not slow. Could I cut the vent line to the tub and add an aav? Driving me crazy!

    • Charles Buell says

      At this point you need to call a plumber. A low spot somewhere can fill with water and would not be cleared by snaking. There are also other possibilities as well, but let the plumber figure it out.

  20. I just bought a beach condo built in the 50s. Mine is on the top floor. It is an effeminacy and I am trying to put in a real kitchen. I tore into a wall that separated a closet and the original kitchenette. There are two brass (I think) vents coming from the floor below. The one vent 90s and connects with the other vent. This area has a drop ceiling. The one vent extends above the drop ceiling then 90s off and it looks like it goes the the condo next door.

    My question is, can I cut the two vents and 90 them towards a wall the run up the wall to connect to vent going into condo next door. The purpose would be to keep all of that below the counter height and run the chase next to an existing wall to open the space where the vents were? I can move the existing water lines very easily.


    • Charles Buell says

      Duane, that is way too complicated to have any opinion of from here. I strongly recommend consulting a licensed plumber. There may even be restrictions as to what you can and cannot do because of its being a Condo. Alterations to buildings of this type really need to be done by qualified parties.

  21. Hi Charles,
    We just bought a house with an ejector pit for the basement bathroom. The initial inspection didn’t show any odors when the pump was cycled but the inspector said that because it was not vented above the roofline but rather out a basment window, a Studor valve would be the way to rectify this issue.

    We asked the homeowner to correct the venting issue and he T-d in a Mini Studor between the ejector and the external vent out the window. We now live in the house and notice a not so fresh sewer smell from around the area.

    Is the vent installed correctly or is this why it stinks all of a sudden? Any tips on what to do to get rid of the smell?

    I’m attaching a photo to try to show what’s going on. Sorry, the basment isn’t well lit in this area so it’s darker than I would like but you can see the external vent going outside and the Studor vent coming up from the original vent pipe.


    • Charles Buell says

      I am a little confused. You said it did not have odors at the time of inspection? Regardless, the vent has to go above the roof line. Why you are getting odors now that you have installed an air admittance valve is odd. It should not go both to atmosphere and have an air admittance valve—needs one or the other. I am pretty sure AAV’s should not be installed on ejector pumps because there would be no way for the air pressures in the tank to equalize. Have the thing vented to a proper location above the roof and you should be good to go. I recommend consulting with a licensed plumber about this.

      • Hi Charles,
        Yes, I thought it odd that it is vented with both the AAV valve and atmosphere now. From my research after the fact it seems that this is not the correct way to do things. I suspected that the homeowner hacked this together to appease us and since we didn’t know any better at the time, we accepted it as the norm. Thanks for the confirmation. We will look into removing the AAV and venting above the roofline instead.

  22. Hi There,
    Your advice would be much appreciated.
    I would like to use an 50mm AAV in place of my 50mm roof vent. I have renovated and are therefore trying to avoid plumbing through the walls and roof space.
    This is the only vent 2/3 along a 10m horizontal (100mm) stretch. It services a toilet, bath, shower, handbasin, kitchen sink and dishwasher.
    It will be positioned 200mm vertically above the horizontal drain and within 1m of the flood line of he highest basin.
    The AAV will be placed under the floor in a storage room.
    Will this be adequate?

    • Charles Buell says

      AAV’s do not eliminate the need for a vent through the roof. If you are talking about an addition to the plumbing system, then an AAV might be able to be installed in the area of the new plumbing but a plumber would need to be consulted as to where it can be installed and if it can be installed. Sorry I can’t be more specific, but these things have to be installed properly.

  23. Hi Charles,

    Thanks very much for this informative article! We have a “drain vent valve” (this doesn’t have a spring in it, just the thin rubber membrane, but i’m assuming it is pretty much the same as the auto-vent you discuss) installed under our sink (see photo) and have looked at replacing it with an AAV. However, as you can see the garbage disposal is installed very close to the pipe, so there isn’t enough space for the AAV, or even enough space for extending the pipe above the disposal.

    Do you have any advice for this? Thanks!

    • Charles Buell says

      Yes, that is an auto-vent and there should be room to replace it with an Air Admittance Valve although the configuration is not quite proper as it is required to be mounted on pipe that cannot be taken apart (white pipe connection to the black pipe). Just have a plumber install a proper one. With only minor adjustments there should be room to do this.

      • When using an AAV, be aware that exhaust fans can create a negative air pressure condition if there is not enough “make-up air”, and the closed AAV will allow the exhaust fan to suck ta trap dry and bring sewer gas into the room.

        • Charles Buell says

          Rufus, this is not how AAV’s work. The more negative pressure at the interior or positive pressure in the drain the tighter the vent seals.

  24. hi. We have a newly constructed home on a septic system. Below both of my kitchen sinks, the vents still emit a disgusting amount of methane. Our plumber replaced the vents with the same ones but less than 30 days later, the gas build up commenced. In as so much that a latex glove is fully inflated all of the time. The vents keep failing. is there a better vent cap that is recommended that will,last more than 30 days.

    • Charles Buell says

      Caryn, you have something very wrong with your venting system. The AAV’s are not failing—something else is wrong. Contact a different plumber. I would look to some sort of total blockage in your main vent through the roof. Let me know what you find out.

  25. Charlie

    Under my kitchen sink I have an AAV, but also another uncapped pipe over a P trap. We think we are getting sewer gas smell when we run the dishwasher. The dishwasher drains to the garbage disposal. See attached photo.

    Thank you.

  26. Hi Charlie,

    today we woke up to a odor coming from our small utility dishwasher ( no sink). We have had no problems for 10 years. it is definitely coming form the vent ( see attached ). is the vent something that needs to be replaced? Thanks.

  27. I have 3 under sink vents in my mobile home and one has an odor. I have replaced it and still have an odor, any idea of the problem?

  28. Brian naylor says

    Hay, I seamed to be getting what smells like sewer gases from under my kitchen sink. I’ve been reading about these AAVs, and believe that is what I have. I feel that it is leaking due to improper install. I think I read that these are supposed to be installed within 10° of fertile. Mine is far from it. Could this cause it to not make a good deal and allow some bypass. I had a septic system, not public sewer. I tried attaching a pic, but it was telling me the file was to large. Is there an email I can send it to, to have you look at it, and give me your opinion?

  29. Hello, I replaced the aav behind the toilet wall that controls the shower toilet and sink on the ground level of the house. The toilet still won’t flush, when I loosen the valve it immediately flushes. Could the new valve be faulty? Flushes just fine without the valve. I know I need one for gases. Could it be anything else. Thanks.

    • Charles Buell says

      I assume you removed the orange rubber band and packing from around the vent? When it is not in place you should be able to suck on the bottom and verify it opens.

  30. We had licensed plumbers install an open tap into our septic line with a trap and 18″ standpipe per code for washing machine discharge to replace an old dry well set up. (That’s an open pipe in the picture, we just have a temporary cap over it until we get it set up properly to keep the trap filled.) The discharge hose just hangs into the open pipe, but the height is close to the maximum the washer will lift. If this doesn’t work due to insufficient lift, can I hard-pipe a laundry pump like the Zoeller into the line and not worry about the trap working since it will be a closed discharge system vented through the pump canister?

    • Charles Buell says

      The ejector pump will need back flow protection as well as an air admittance valve and the trap will go away. That may be the hard part as no pipe has been left to connect to. The current arrangement is likely to be problematic due to height.

      • Thanks! I called a plumber to come and look at it. Th Zoeller pump gets 19′ of discharge head so height should not be a problem as long as I can get the venting set up right. A check valve comes with the pump for backflow protection.

  31. When the temperature drops below freezing we get a smell in the house, the furnace is on so its difficult to figure out where the smell is coming from. We have a new cheater vent under the kitchen sink, the smell is not coming from there. We also have a powder room on an outside wall , so its a chilly little room. If that bathroom has a cheater vent is it possible that it stops venting in cold weather?

    • Charles Buell says

      Unfortunately I am not going to be of much help. The cheater vent should be fine in the cold, so I think you have something else going on and you should call a good plumber.

  32. I have a question….We built a house last year and we have been in it now a year and three months and we have been up in the attic 100 times already but yesterday I went up there and noticed a sewage smell…upon inspection from my husband he seen where on of the sewage pipes was not vented. We have contacted our builder and he says it was supposed to be capped and he’d contact the plumber to come take care of it in a few days. Well he’s contacted me and says that he will come this afternoon to put an automatic vent on there…he claims that he doesn’t normally vent out of the roof with a metal roof. My question is first…has this been dangerous on our health with the pipes leaking this all this time and us having no idea…are their gases being leaked from these pipes that we have been inhaling all this time? And 2nd shouldn’t this be vented outside of the house thru the roof? Is the auto vent sufficient? And why would we be just now smelling this after all this time? I know that we have to add more lines to our septic tank and that we’ll smell it outside from time to time because of that but the inside is what worries me and I want to make sure that our plumber is doing what needs to be done. Thanks so much for your help!

    • Charles Buell says

      At least one of your plumbing system vents must go through the roof, if this vent in the attic is the ONLY vent you have then no, installation of an AAV would not be appropriate. As to health concerns, those gases would typically go out the roof vents and not end up indoors. There is also a difference between an air admittance valve and an auto vent so if it turns out that an AAV is ok and is going to be used, make sure it is not an auto vent (has a spring in it). There can be all kinds of reasons why you are only smelling it now, weather inversions etc. Septic systems typically produce much more vent odors than city systems—so there is that too.


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