Running Plumbing Vents Through Walls vs. Roofs
Plumbing vents through the wall instead of roof downsides?
Hey all,
Ive got 7″ of polyiso on the roof with metal and looking at doing the plumbing vents through the wall instead of roof penetrations. Its a 2 story house and the vents would be 10′ from any open window so should pass code. I can’t see any downsides to this, so figured id see if anyone has any advice why i shouldn’t do this.
Also on that venting note, there’s two bathrooms on opposite sides of the house, so was thinking id do two separate 2″ vents instead of trying to connect everything to a main 3″ vent. One side would be a master bath on a 2″ vent and the other side would be a kids bath with laundry below it on a separate 2″. The kitchen sink is in an island so doing a AAV and there is an additional bathroom in the basement that I was going to do an AAV as well. If that AAV is on the sink, will that vent properly the toilet and shower?
thanks once again, this forum is truly the best.
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Replies
You need to make sure you aren’t venting under soffit with vent, and that it is high enough. Also when using aav just be aware of positive pressures. There are guidelines for how to properly vent a house using aav that you should take a look at. Without really knowing lengths dfu and sizing it’s hard to say if you need additional venting for shower and toilet. I would consider having a plumber at least consult on your proposed design, though I’m not sure if you will have much luck finding one to just consult.
Also another note: while 10’ may be adequate, there is a much higher chance that smells will get caught and waft under a soffit to open windows. I don’t think I would vent on a wall with any operable windows, but it may be fine
thanks for your reply, its an unvented roof so no soffit intake vents. Also its on the 2nd story above a secondary 1st story side roof. Its about 12' from a kids window.
I wish i could find a plumber that could consult me... Had 2 quotes come in at $24 and 26k for 3 bath, 1 kitchen.... Both had never installed uponor pex and one wanted to drill big holes through some structual beams... So here I am doing it myself.
Oregon does allow AAV providing there's at least 1 main vent as well
You should reach out to an MEP engineer. They generally do commercial as that is where it’s required but they will probably draw you a plan. It will cost a couple thousand but I would say definitely worth it to get it right.
AAV for a toilet? I don't think so, no?
I talked my plumber into doing a loop vent for my powder room so I wouldn't have to put another hole in my brand new roof, and I think the distance was iffy. Only toilet that might flush funny....
Just punch the holes where they need be and flash them the right way
You can vent a toilet with an aav but you still need a main vent stack, as the aav does not vent positive pressure, which you can/will get with a toilet flush. I’m not sure why you used a loop vent for your toilet but I have never heard of that. You actually may want to add an aav if it flushes funny.
For the op you should talk with your inspector and municipality as some do not like aav.
Here is an info graphic from oatey https://www.oatey.com/faqs-blog-videos-case-studies/blog/3-things-you-should-know-about-air-admittance-valves
I could be wrong, or outdated, or it could just be in my state, but it was my recollection that AAVs are only used where you need an AAV, not where you want an AAV.
An island sink might need an AAV.
I have never seen or even heard of one in Massachusetts that wasn't on an island sink
I don’t know how you could even write something like this into the code. There is no code requirement to only allow aav on islands in icc. Also you can vent an island with a loop vent so is this somewhere it’s actually needed and not just wanted?
Anyways you can use aav as long as you abide by code requirements, and there are no code requirements saying you need to prefer other methods of venting (unless it’s some local adoption)
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“I can’t see any downsides to this”
When you put the vent pipe in a cold location like an exterior wall you are required to use a larger diameter pipe that will displace insulation from the wall and the pipe will be filled with cold air. This will make a cool spot on the drywall it may well fall below the dewpoint of the air in the house sometimes and get wet maybe even grow mold.
I understand that you want to reduce the roof penetrations but if your roofer is so incompetent that the vent pipes leak you need a new roofer.
Walta
And if your plumber can't tie all the vents together into a single vent through the roof, you need a new plumber!
AS someone with a whole house with no ceilings, it can get complex, but yeah, we managed it in a remodel adding a half bath and moving a sink, so it is not that hard
The whole 2nd story is vaulted ceilings, no dropped ceilings. The bathrooms are vaulted as well and insulated above the 2x6 T&G ceiling so there's no attic to easily connect all vent pipes to a single vent. The master is on the other side of the plumbing main stack.
I'm the roofer and the plumber haha. I can flash a vent pipe but thought maybe going through the wall would be easier and avoid having to bore through 10" of material.
I do see your point on the cold spot with the wall insulation. The walls will have polyiso on the exterior but I guess that doesn't really matter? The roof would displace the 7" of polyiso as well so not quite sure what the difference is still.
A while back I had to connect two stacks from opposite side of the house to a single vent through a cathedral ceiling. Was about 22' run of 2" ABS pipe crossing through 3 9.5" I-joists bays. Takes a bit of planning to get the slope correct and lot of the wall top plate go hogged out to recess the first elbow, other than that it wasn't that hard. Still plenty of room for fluffy insulation around the vent pipe.
A roof vent also means you can easily get up there and snake the stack in case it is needed.
Wunderbar,
FWIW, I have a single side wall vent that satisfies the one "wet" vent rule I faced. Everything in the house is AAV which saved a nightmare of pipe runs that would have been stymied by large beams. My roof is very low pitch with 8+ inches of EPS nailbase and membrane on that. Needless to say I was not looking to poke a hole in it for a vent pipe.
A few things to note six years in. Plan on cleaning hair out of bath sink traps and the first drop after the trap. Lovely long hair globs will grow over time and cause the AAV to make gasping noises if the globs get to the vertical drop. All the AAV's make very small sounds if you are paying close attention or are on the wall side where I placed them. Use the box pockets with grilles to dress them up and make future replacement a snap. I put most of them in closets that shared a wall with the baths. The one straight to outdoors or "wet" vent is tied to the washing machine discharge point. I would have to dig out the construction photos to see if the toilets are also tied to the same run.
In traditional roof vents the pitch of horizontal runs are set to carry condensate back to the main stack. In my opinion I risk less cold air intrusion by strongly pitching to the outside and to ensure the condensate runs out. If I pitched inward I believe the cold flow inward could cause condensate to freeze right at the outside limit. It could create an ice damn situation that might eventually block the vent. Running the warm condensate outward has worked for me so far. However, I should note that I had a vertical vent freeze over during a prolonged subzero winter in Chicago, so take your pick.
Draining outward can create staining on a metal roof, but my roof is meant to rust, so it is not noticeable. Icicles can form at the vent mouth in winter, but my roof is more prone to icicles due to the lack of gutters. The risk of sewer gas smell will depend heavily on how the wind moves around the house. We have noted a few wiffs at ground level when certain winds arrive (from the west in our case). As long as you are away from operable windows I would think you are safe.
Mostly be sure your inspector is down with your plans.
I'd rather have multiple roof penetrations if that avoids horizontal runs in the vents. That's where you get the obstructions, where they freeze, and they are a lot harder to clear.
The issue I've found with horizontal runs is sagging over time. This is more of an issue with cellular ABS which tends to sag a lot more over time. If using that, I would put extra supports along the way.
Vents run inside cathedral ceiling tend to be near room temperature, so they won't freeze. You do have to make sure there is enough slope to drain.
An extra roof vent is not that big of a deal unless it will be in the way of future PV array.
Even with a vaulted ceiling you can create opportunities to hide vent pipe. Chases, faux beams, faux posts, dropped ceiling to create a service cavity, etc. Get creative and you can avoid the pipe out the wall.