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Venting through soil stack?

2976 Views 11 Replies 6 Participants Last post by  SectorSecurity
I am in the process of adding a bathroom in my basement and I am trying to figure out how my house is vented. The house was built in the early 70's and as far as I can tell there is no vents going through the roof, unless they tied into the whirley bird meant to vent the attic.

I can see where the waste lines in the bathroom are connected to the main soil stack which runs back into the basement and out into the sewer.

Is it possible they extended the soil stack into the attic and vented all the fixtures that way?

I have looked and do not see any vent lines coming off the bathroom sink or kitchen sink.

I haven't popped into the attic yet to see what is going on up there, but I am not sure what I am missing?

Is it acceptable to vent using the soil stack if it extends into the attic(and hopefully through the roof)?
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Depending on many restrictions, yes.... you could have "wet venting" where the main soil stack acts as a vent also.

Operative here is many restrictions in the configuration... trap arm lengths/sizing, single floor etc etc.

Would need to know your exact layout to know if it even possible.... it does seem unlikely that the entire house (multi bath rooms and kitchen/washer.... etc could all be wet vented.....

Get up on the roof and determine your main vent and other vents.....


EDIT: Studor AAV venting is also a possibility depending on your jurisdiction.... although I think most jurisdictions that allow them, also require them to be accesable.... so you ought to be able to get to them or see them.

(Caveat.... I'm a GC not a plumber. If I do minor plumbing myself, I have to pull out my books and review anything but simple venting.)

Of course venting may be tied into other dry vents and projections thru the roof can be minimized.
It's not completely foreign to see houses with AAVs instead of vent pipes either.
Depending on many restrictions, yes.... you could have "wet venting" where the main soil stack acts as a vent also.

Operative here is many restrictions in the configuration... trap arm lengths/sizing, single floor etc etc.

Would need to know your exact layout to know if it even possible.... it does seem unlikely that the entire house (multi bath rooms and kitchen/washer.... etc could all be wet vented.....

Get up on the roof and determine your main vent and other vents.....

Of course venting may be tied into other dry vents and projections thru the roof can be minimized.
I was thinking there may be an AAV(s) somewhere that I have missed, will have to do more poking around.

I did figure it would be strange for a 3 piece washroom, kitchen sink, washer and laundry tub to be wet vented. Although in this house wouldn't surprise me.
It's not completely foreign to see houses with AAVs instead of vent pipes either.
I am thinking the main stack goes into the attic and has a valve on it and they figured because the attic is vented through a wind turbine no need to go through the roof with the pipe. Will have to get out the ladder and pop my head into the attic and see what is up there.
Interesting.... never seen/heard of a studor main stack vent...

Anyone know about that assembly?????????
I am thinking the main stack goes into the attic and has a valve on it and they figured because the attic is vented through a wind turbine no need to go through the roof with the pipe. Will have to get out the ladder and pop my head into the attic and see what is up there.
I am thinking when I plumb the basement I am just going to put an AAV under the sink and skip worrying about venting to the roof.

Although I am still curious how the rest of the house is vented.
It would be right at the fixture, hard to miss. A bath can be wet vented.

We need Mike back to sketch this out.
I was thinking there may be an AAV(s) somewhere that I have missed, will have to do more poking around.

I did figure it would be strange for a 3 piece washroom, kitchen sink, washer and laundry tub to be wet vented. Although in this house wouldn't surprise me.
I remodeled a couple of condos in a complex and there was only one common stack for each "tower" of five floors. Vents were in the ceiling and were always tied back into that same stack.

I thought that was normal.
We have plenty of Philadelphia single stack systems in place around these parts which rely on one main 4" stack vent through the roof and one lawn/curb vent riser which serves 3 floors. S-traps were the norm and these systems are still functioning today.

The single stack at my house was 72 years old before I ripped everything out during rehab and vented it to modern standards.

Obviously your main stack is your vent, probably just terminates in the attic otherwise you'd be sucking your traps dry and living in stench.
Once a soils stack extends vertically above the highest fixture served it becomes a vent stack.
Thanks for all the info guys, I think I am going to go the AAV route in the basement as we just put in new floors and finished painting and I dont think the girlfriend will let me start ripping out walls to run a vent stack.
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